API Automotive Gear Oil Classifications OilChat#13

The API (American Petroleum Institute) defines automotive gear lubricant service designations to assist manufacturers and users of automotive equipment in the selection of transmission, transaxle and axle lubricants based on gear design and operating conditions.

Selecting a lubricant for specific applications involves careful consideration of the operating conditions and the chemical and physical characteristics of the lubricant. The API designations also recognize the possibility that lubricants may be developed for more than one service classification.

Gear oils are classified by the API using the letters GL (abbreviation for Gear Lubricant) followed by a number to identify the performance level of the oil. The API has also issued the MT-1 service designation for certain non-synchronised manual transmissions. Only three of the seven automotive gear lubricant service designations issued by the API are currently in use due to changes in manufacturers’ recommended practices or due to the unavailability of testing hardware.

The API Lubricant Service Designations for Automotive Manual Transmissions, Manual Transaxles, and Axles are described below, followed in some instances by supplemental comments (in italics) regarding the use of these lubricants:

API GL-1 (Obsolete)

This designation denotes lubricants intended for manual transmissions operating under such mild conditions that straight petroleum or refined petroleum oil may be used satisfactorily. Oxidation and rust inhibitors, antifoam agents and pour depressants may be added to improve the characteristics of these lubricants. Friction modifiers and extreme pressure additives shall not be used.

API GL-1 lubricants are generally not suitable for most passenger car manual transmissions. However, these
oils may be used satisfactorily in some truck and tractor manual transmissions. Lubricants meeting service designation API MT-1 are an upgrade in performance over lubricants meeting API GL-1 and are preferred by commercial vehicle manual transmission manufacturers.

API GL-2 (Obsolete)

The designation API GL-2 denotes lubricants intended for automotive worm-gear axles operating under such conditions of load, temperature, and sliding velocities that lubricants satisfactory for API GL-1 service will not suffice. Products suited for this type of service contain anti-wear or film-strength improvers specifically designed to protect worm gears.

 

API GL-3 (Obsolete)

This designation denotes lubricants intended for manual transmissions operating under moderate to
severe conditions and spiral-bevel axles operating under mild to moderate conditions of speed and load. These
service conditions require a lubricant having load-carrying capacities exceeding those satisfying API GL-1 service
but below the requirements of lubricants satisfying API GL-4 service.

Gear lubricants designated for API GL-3 service are not intended for axles with hypoid gears. Some transmission
and axle manufacturers specify engine oils for this service.

 API GL-4 (Current)

The designation API GL-4 denotes lubricants intended for axles with spiral bevel gears operating under moderate
to severe conditions of speed and load, or axles with hypoid gears operating under moderate conditions of speed
and load. Axles equipped with limited-slip differentials have additional frictional requirements that are normally
defined by the axle manufacturer.

API GL-4 oils may be used in selected manual transmission and transaxle applications where API MT-1 lubricants
are unsuitable. In all cases, the equipment manufacturer’s specific lubricant quality recommendations should be
followed.

API GL-5 (Current)

This designation denotes lubricants intended for gears, particularly hypoid gears, in axles operating
under various combinations of high-speed/shock load and low-speed/high-torque conditions. Frictional requirements for axles equipped with limited-slip differentials are normally defined by the axle manufacturer.

API GL-6 (Obsolete)

The designation API GL-6 denotes lubricants intended for gears designed with a very high pinion offset. Such
designs typically require protection from gear scoring in excess of that provided by API GL-5 gear oils.

A shift to more modest pinion offsets and the obsolescence of original API GL-6 test equipment and procedures have eliminated the commercial use of API GL-6 gear lubricants.

API MT-1 (Current)

This designation denotes lubricants intended for non-synchronized manual transmissions used in buses
and heavy-duty trucks. Lubricants meeting the requirements of API MT-1 service provide protection against the
combination of thermal degradation, component wear, and oil-seal deterioration, which is not provided by lubricants in current use meeting only the requirements of API GL-4 or GL-5.

API MT-1 does not address the performance requirements of synchronized transmissions and transaxles in
passenger cars and heavy-duty applications.

Automatic or semi-automatic transmissions, fluid couplings, torque converters, and tractor transmissions usually require special lubricants. Consult the equipment manufacturer or your lubricant supplier for the proper lubricant for these applications.

The API Automotive Gear Oil Classifications only specify performance level and service designation. Viscosity limits for automotive gear lubricants are described by the SAE J306 standard as discussed in OilChat #4.

ACEA Oil Sequences (part 2) OilChat#12

The ACEA Oil Sequences describe, amid others, “E” category service-fill oils for heavy duty diesel engines. These sequences define the minimum performance level for engine oils to meet ACEA requirements. Performance parameters other than those covered by the sequences or more stringent limits, may be specified by individual engine manufacturers – hence OEM specifications such as Mercedes-Benz 228.3, Volvo VDS-3, etc.

The ACEA Oil Sequences are subject to constant development to stay abreast of new engine designs, the increasing use of biofuels and more stringent emission requirements.

Each new issue of the sequences may exclude a previous sequence or include a new one, incorporate an increase in severity for an existing sequence or a change in testing method. As new editions are published older editions are withdrawn. The table below summarises the changes that have occurred since the first ACEA Oil Sequences were introduced in 1996.

 

ACEA intentionally omitted “E8” from the sequences.

A change in year linked to a specific sequence (i.e. E4-99 to E4-07) in the table above indicates a change in the sequence requirements. The four current ACEA Oil Sequences for heavy duty diesel engines are described below followed by a brief outline of the relevance of the sequence in italics:

E4 Stable, stay-in-grade oil providing excellent control of piston cleanliness, wear, soot handling and lubricant stability. It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV and Euro V emission requirements and running under very severe conditions, e.g. significantly extended oil drain intervals according to the manufacturer’s recommendations. It is suitable for engines without particulate filters, and for some EGR (Exhaust Gas Recirculation) engines and some engines fitted with SCR NOx (Selective Catalytic Nitrogen Oxides) reduction systems.

UHPD (Ultra High Performance Diesel) category and the highest level of engine oil performance in the global heavy duty diesel market. Mostly SAE 10W-40 formulated with Group III base oils. Extended drain oils suitable for use in vehicles without a DPF (Diesel Particulate Filter). 

E6 Stable, stay-in-grade oil providing excellent control of piston cleanliness, wear, soot handling and lubricant stability. It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV, Euro V and Euro VI emission requirements and running under very severe conditions, e.g. significantly extended oil drain intervals according to the manufacturer’s recommendations. It is suitable for EGR engines, with or without particulate filters, and for engines fitted with SCR NOx reduction systems. Designed for use in combination with low sulphur diesel fuel.

UHPD category and the highest level of engine oil performance seen in the global heavy duty diesel market. Mostly SAE 10W-40 formulated with Group III base oils. Extended drain low SAPS oils suitable for use in vehicles with or without a DPF.

E7 Stable, stay-in-grade oil providing effective control with respect to piston cleanliness and bore polishing. It further provides excellent wear control, soot handling and lubricant stability. It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV and Euro V emission requirements and running under severe conditions, e.g. extended oil drain intervals according to the manufacturer’s recommendations. It is suitable for engines without particulate filters, and for most EGR engines and most engines fitted with SCR NOx reduction systems.

SHPD (Super High Performance Diesel) tier of mainly SAE 15W-40 engine oils designed for use in medium severity operations. Suitable for use in vehicles without a DPF. Often combined with API CI-4. 

E9 Stable, stay-in-grade oil providing effective control with respect to piston cleanliness and bore polishing. It further provides excellent wear control, soot handling and lubricant stability. It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV, Euro V and Euro VI emission requirements and running under severe conditions, e.g. extended oil drain intervals according to the manufacturer’s recommendations. It is suitable for engines with or without particulate filters, and for most EGR engines and for most engines fitted with SCR NOx reduction systems. Designed for use in combination with low sulphur diesel fuel.

SHPD tier of mainly SAE 15W-40 engine oils designed for use in medium severity operations. Suitable for use in vehicles with and without a DPF. Often combined with API CJ-4. 

Claims against the ACEA Oil Sequences can be made on a self-certification basis. ACEA, however, requires that any claims for oil performance relating to these sequences must be based on credible data and controlled tests in accredited test facilities.

It is expected that new ACEA Oil Sequences will be issued during the third quarter of 2016. ACEA 2016 marks the first update since 2012, a break from the specification’s typical biennial update schedule. So what are some of the sequence changes that we can expect to see in ACEA 2016?

Biofuels. New fuel alternatives are becoming increasingly prominent, particularly the use of biodiesel fuels for the heavy duty market. These fuels can lead to increased oxidation, degradation and thickening of the oil. ACEA 2016 may therefore include new tests to assess lubricant effectiveness to prevent oxidation and deposit formation.

Seal Materials. Modern engines have introduced new elastomer sealing materials, necessitating an update of the seal test methods in ACEA 2016.

Soot. A new test may possible be added to assess oil resistance to soot-related thickening and deposits in diesel engines. The expected test will reflect the cleaner operation of modern low-soot heavy duty diesel engine oils.

In summary, modern diesel engines are being forced to become more fuel efficient, less polluting, and longer lasting. Subsequently their lubrication needs have changed dramatically since 2012. In addition, oil change intervals are being extended and the use of biodiesel is increasing. These changes require the use of superior heavy duty diesel engine oils. ACEA 2016 is expected to address all these issues and it is therefore not surprising that its pending release is anticipated globally with great interest.

Oil Chat will keep you UpToDate.

Always consult your vehicle owner’s manual to determine what engine oil you should use, and READ THE LABELS ON THE OIL YOU BUY.

ACEA Oil Sequences (part 1) OilChat#11

ACEA is the abbreviation for the Association des Constructeurs Européens d’Automobiles or the European Automobile Manufacturers’ Association in English. Among many other activities ACEA defines specifications for engine oils on behalf of the major vehicle manufacturers in the European Union.

The ACEA Oil Sequences were introduced in 1996 when they superseded the former CCMC (Committee of Common Market Automobile Constructors) specifications for engine oils. The ACEA Oil Sequences are the European counterpart of the API Engine Oil Classification System.

There are three principal categories within the ACEA Oil Sequences – “A/B” for petrol and light duty diesel engine oils, “C” for light duty catalyst compatible oils and “E” for heavy duty diesel engine oils. In this issue of OilChat the ACEA Oil Sequences for petrol and light duty diesel engines will be discussed. However, before this is done a few terms that are used in describing the Sequences need to be explained:

SAPS: (Sulphated Ash, Phosphorus, Sulphur) Phosphorus and sulphur comprise a significant portion of the additive content of engine oil. Sulphated ash is not added to oil; it is the result of additives in the oil leaving an ash residue when the oil is burnt under prescribed laboratory conditions.
DPF: (Diesel Particulate Filter) A device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine.
TWC: (Three Way Catalyst) A catalytic converter that reduces the harmful Nitrogen Oxides, Carbon Monoxide and Unburned Hydrocarbons in the exhaust gas of (mainly petrol) engines.
HTHS: (High Temperature/High Shear rate viscosity) HTHS is indicative of the resistance of engine oil to flow in the tight tolerances between fast moving components in hot engines. It influences fuel consumption and wear in high shear regimes in an engine, such as those existing in piston ring/cylinder wall interface and the valve drive train. Lower HTHS viscosity generally means thinner oil which can improve fuel economy. Lower HTHS viscosity, however, usually comes at the expense of wear protection and therefore low HTHS oils are not suitable for use in all engines.

 

The current ACEA Oil Sequences were introduced in 2012 and may be condensed as follows:

ACEA A/B : Petrol and diesel engine oils

A1/B1 Fuel efficient oil for use at extended drain intervals in petrol and light duty diesel engines designed to use low friction, low viscosity and low HTHS oils. Unsuitable for use in some engines.

A3/B3 Intended oil for use in high performance petrol and light diesel engines and for extended drain intervals where specified by the engine manufacturer.

A3/B4 Intended for use in high performance petrol and direct injection diesel engines, but also suitable for applications described under A3/B3.

A5/B5 Fuel efficient oil for use at extended drain intervals in high performance petrol and light diesel engines requiring low friction, low viscosity and low HTHS oils. Unsuitable for use in some engines.

ACEA C : Catalyst compatibility oils

C1 Fuel efficient oil intended for vehicles with DPF and TWC. Formulated for high performance petrol and light diesel engines requiring low friction, low viscosity, low SAPS and low HTHS oils. These oils have a SAPS limit of 0.5% and are unsuitable for use in some engines.

C2 Fuel efficient oil intended for vehicles with DPF and TWC. Formulated for high performance petrol and light diesel engines designed to use low friction, low viscosity and low HTHS oils. These oils have a SAPS limit of 0.8% and are unsuitable for use in some engines.

C3 Fuel efficient oil intended for vehicles with DPF and TWC. Formulated for high performance petrol and light diesel engines designed to use low HTHS oils. These oils have a SAPS limit of 0.8% and are unsuitable for use in some engines.

C4 Fuel efficient oil intended for vehicles with DPF and TWC. Formulated for high performance petrol and light diesel engines requiring low SAPS and low HTHS oils. These oils have a SAPS limit of 0.5% and are unsuitable for use in some engines.

Note: Oils with a 0.8% SAPS limit may be referred to as mid SAPS.

To meet the stringent requirements of the above ACEA Oil Sequences, engine oils must pass fourteen laboratory and ten engine tests. Hence oils that conform to these ACEA standards are formulated with superior additive packages – even more so when the oil needs to meet API requirements as well. For instance, a well formulated engine oil can conform to ACEA A3/B4/C3 as well as API SM/SN. It is, however, not always possible for an oil to meet both ACEA and API standards. To illustrate, it is unattainable for an ACEA A5/B5/C1 performance level oil to meet API SM/SN, because A5/B5/C1 requires a maximum phosphorus limit of 0.05% whilst SM/SN specifies a minimum level of 0.06%.

Since the first ACEA Oil Sequences were introduced in 1996 new specifications were issued in 1998, 1999, 2002, 2004, 2007, 2008, 2010 and 2012. It is therefore obvious that the next issue of the ACEA Oil Sequences is now long overdue. Reasons for this delay are the replacement of obsolete tests with new ones to reflect engine technology advancements and also to address the complications associated with the increasing use of biofuels. It is expected that the new sequences will be issued during the second half of 2016 and that the new release may, among other changes, comprise the removal of A1/B1 and the introduction of a C5 category.

The ACEA Oil Sequences represent some of the most significant performance standards of the lubricant industry. Their influence and importance extend beyond Europe and since the pending update is a major step for the global lubricant industry, it is anticipated with great interest.

In conclusion it should be mentioned that ACEA itself does not test or approve any oils. They set the standards and oil manufacturers are responsible for having their oils tested in accordance to the prescribed standards. They may then make performance claims for their products, provided such products satisfy the relevant ACEA requirements.

Always consult your vehicle owner’s manual to determine what engine oil you should use, and READ THE LABELS ON THE OIL YOU BUY.

AQ8OILS Blending Plant ANTWERP, Belgium OilChat#10

Q8Oils’ state-of-the-art blending plant in Antwerp is one of the largest and most technically advanced lubricant production facilities in Europe. With a multi-million Euro investment just completed, the plant has a blending capacity which is scalable up to 250 million liters per annum.

With 24 base oil and 42 additive tanks respectively, the plant can efficiently produce the widest range of finished lubricant products of any blending plant in Europe. Furthermore the mega-blend vessel at Q8Oils’ Antwerp blending plant can manufacture batches up to 400,000 liters.

 

Q8Oils is a subsidiary of the Kuwait Petroleum Corporation (KPC), one of the world’s largest oil producers. Supported by KPC’s significant resources, Q8Oils is a leading global lubricants supplier. Q8Oils offers one of the most comprehensive ranges of lubricants in the industry, with a portfolio of more than 1,000 different products to suit every application from the smallest consumer to the largest machines.

Q8Oils product innovation and exceptional quality are achieved by combining the latest additive technologies with superior base oils. This is supported by O8Oils Antwerp plant’s stringent in-house quality control procedures and world-class technical development capabilities that are complemented by ISO 9001, ISO 14001 and RC 14001 certification.

To find out more about the plant go to our homepage, click on the NEWS tab and open Kuwait Petroleum’s Q8Oils opens its state-of-the-art Blending Plant in Antwerp.

The link below will take you on a visual tour of the plant…..

Q8 Blending Plant.mp4

 

 

 

API Diesel Engine Oil Classifications OilChat#9

The American Petroleum Institute (API) Engine Oil Licensing and Certification System provides a simple designation of letters and numbers that allows engine manufacturers and oil marketers to provide users with the information they need to ensure that the proper oil is selected for an engine.

Each letter/number designation identifies a service category (e.g. CI-4) which is linked to a series of tests that the oil must pass before it is allowed to carry that designation. The API “S” series describes oil standards for petrol engines (see OilChat #8) while the API “C” series defines oil standards for diesel engines as summarised in the table below:

 

One of the reasons for the obsolescence of the older categories is a lack of facilities and parts to run some of the key engine tests required for qualification. API Oil Service Categories CA, CB and CC should no longer be used in diesel engines unless specifically recommended by the equipment manufacturer.

 

API released the ‘intermediate’ category CI-4 Plus during 2004 as corrective action to tweak CI-4 since these oils were not performing as they were originally intended to do in all applications.  CI-4 PLUS closes a small but very real gap between the expected conditions of 2002 low-emission engines and what was actually taking place in the real world.

 

By consent decree engine manufacturers were required to comply with the US Environmental Protection Agency (EPA) emission standards set for 2004 as early as from October 2002, 15 months ahead of the scheduled date. As a result, both engine manufacturers and lubricant formulators had to alter their product development timelines drastically. In fact the CI-4 category was only finalized in December 2001, a mere ten months before the revised introduction date of the new low-emission engines. That created a situation where 2002 engines were being designed and developed parallel to the oil, rather than in sequence. Actually CI-4 was the first oil to be developed without engines being available to test prototype oils. Although CI-4 proved to be generally effective, oil companies and engine OEMs found that in some instances the soot being generated by cooled Exhaust Gas Recirculation (EGR) was much higher than expected. In addition, it was practically a different kind of soot that thickened the oil much more rapidly. A few OEM’s also discovered that certain engines required better oil shear stability than that specified by CI-4. Consequently CI-4 oil formulations had to be adjusted to handle what was happening out in the field and API CI-4 Plus was introduced in 2004.

 

 

CI-4 Plus was designed to offer better viscosity control, greater soot loading capability and improved shear stability. Another benefit of CI-4 PLUS is its potential to extend oil drain intervals. However, CI-4 PLUS oils come with a price premium over CI-4 and therefore CI-4 PLUS only benefits a limited percentage of the market. API CI-4 Plus was superseded in 2006 by CJ-4 oils with additive systems specially designed to improve the protection of both the engine and advanced emissions control systems.

 

API is scheduled to introduce two new diesel engine oil categories late 2016 / early 2017. These are API CK-4 and API FA-4.  This is the first time since 1994 that an API diesel engine oil standard has been split into two categories. Part of the impetus for this deviation stems from U.S. EPA regulations to reduce greenhouse gas (GHG) emissions and improve fuel economy for diesel engines. The new categories are created to address these mandates, enabling new advancements in diesel engine design, improving fuel economy through the use of lighter viscosity oils and enhancing engine durability through improved additive chemistry, as well as base oil selection.

Performance criteria for API CK-4 and FA-4 are summarized below:

API CK-4 describes oils for use in high speed four-stroke diesel engines designed to meet 2017 model year on-highway and Tier 4 off-road exhaust emission standards, as well as for previous model year diesel engines.

 

API FA-4 describes certain XW-30 oils specifically formulated for use in on-highway, high speed four-stroke diesel engines designed to meet 2017 model year on-highway greenhouse gas (GHG) emission standards.

Finally it should be mentioned that it is possible for engine oil to conform to both API diesel and petrol standards. It is common that diesel rated engine oils carry “corresponding” petrol specifications. For example, API CJ-4 oils will almost always list either SL or SM, while API CI-4 will normally conform to SL and API CH-4 oils will usually meet SJ, etcetera.

Always consult your vehicle owner’s manual to determine what motor oil you should use, and READ THE LABELS ON THE OIL YOU BUY

 

 

API Petrol Engine Oil Classifications OilChat#8

In the early days of the automobile, engine oils were classified by viscosity grade only. By 1930 vehicle manufacturers, however, recognised that there was a need for fixed standards of lubricant quality so that cars and trucks could be sold anywhere world-wide without major modifications or embarrassing failures.

The American Petroleum Institute (API) then took on the task of setting standards for engine oil. Their first attempt described three oil categories: Regular (straight mineral oil); Premium (mineral oil with oxidation inhibitors) and Heavy Duty (mineral oil with oxidation inhibitors and detergents/dispersants).

However it was soon realised the requirements for petrol and diesel engines were different and the next API engine oil classifications defined categories for petrol (ML, MM, MS) and diesel (DG, DM, DS) engine oils.

Since then the API Engine Oil Classifications have been revised and updated on various occasions to accommodate improvements in engine designs and the ever increasing stresses placed on engine oil, and more recently to address the concern over the environmental impact of engine emissions. Currently the system includes classifications for spark ignition/petrol engines (“S” series) and for compression ignition/diesel engines (“C” Series). Following is the complete classification for petrol engine oils:

CATEGORY STATUS SERVICE
SA
Before 1930
Obsolete Category for such mild service that these oils required no additives. Originally these oils were classified “API Regular”.
SB
1930
Obsolete Formulated to provide some antioxidant and anti-scuff properties. Because this category contained no detergent additives, they were also called “non-detergent” oils.
SC
1951
Obsolete This category provided improved protection against low temperature sludge, deposits, rust, corrosion and wear. Previously known as “API MS”.
SD
1967
Obsolete Engine tests for this classification also included testing the cleanliness of the positive crankcase ventilation valves during short trips and stop-and-go driving.
SE
1971
Obsolete Oils designed for this service provided more protection against oil oxidation, high temperature engine deposits as well as rust and oxidation.
SF
1979
Obsolete Provided improved oxidation stability and anti-wear performance. These oils also offered better protection for smaller, higher revving engines operating at higher temperatures.
SG
1988
Obsolete Oils meeting this service category provided better control of engine wear, oil oxidation, sludge and varnish for improved engine cleanliness
SH
1993
Obsolete These oils offered better protection than previous categories in the areas of deposit control, oil oxidation, wear, as well as rust and corrosion.
SJ
1996
Current This category exhibited different evaporation loss characteristics, plus meeting the requirements of bench tests for wet filterability, gelation index, high temperature foaming and high temperature deposits. SJ also introduced a 0.10 mass % limit on phosphorus content for improved catalyst compatibility.
SL
2001
Current These oils were formulated to provide better high temperature deposit control and lower oil consumption.
SM
2004
Current Designed to provide improved oxidation resistance, enhanced deposit protection, better wear protection, and improved low temperature performance over the life of the oil.
SN
2011
Current Improved high temperature deposit protection for pistons, more stringent sludge control and seal compatibility. Better fuel economy, turbocharger protection and emission control system compatibility.

API intentionally omitted “SI” and “SK” from the sequence of categories since SI is reserved for Système International d’Unités and SK is the brand name of a South Korean oil company.

For automotive petrol engines, the latest engine oil service category includes the performance properties of earlier categories. If an owner’s manual calls for API SJ, SL or SM oil, API SN oil will provide complete protection.

It is expected that the next API standards for petrol engine oils will be available late 2017/early 2018. Some of these next generation oils will have lower multi-viscosity ratings such as 0W-16 (please refer to OilChat #3) to reduce friction for improved fuel economy. They will also include special additive packages to reduce engine wear. These oils are being developed for high output turbocharged gasoline (petrol) direct injection (GDI) engines. API has not yet confirmed the letter designation for the new oil classification, but it will likely be “SP” (skipping “SO”).

In the next issue of OilChat we will address the API classifications for diesel engine oils.

 

Always consult your vehicle owner’s manual to determine what motor oil you should use, and READ THE LABELS ON THE OIL YOU BUY.

Engine Oil Composition OilChat#7

The prime functions of engine oil are to lubricate, cool, clean, protect and seal. In the early days of the automobile neat mineral oil was used to perform these functions. Improvements in engine design and engineering techniques soon lead to parts being manufactured to finer tolerances, higher engine operating temperatures, more power and increased speeds.

Consequently, lubrication problems started to occur. Oils deteriorated rapidly, wear rates increased, engines failed and performance was generally unacceptable. In the early 1900s it was discovered that the addition of chemicals, referred to as additives, could improve the performance of the mineral base oils.

Oils deteriorated rapidly, wear rates increased, engines failed and performance was generally unacceptable. In the early 1900s it was discovered that the addition of chemicals, referred to as additives, could improve the performance of the mineral base oils.

Today engine oils may contain anything between 3% additives in a basic monograde oil and up to 30% in a superior high performance multigrade lubricant. Following is a typical composition of a modern good quality multigrade engine oil:

The base oil component of engine oils may be mineral, synthetic or semisynthetic (a mixture of mineral and synthetic stocks). Most lubricants sold today are still blended using mineral base oils. Synthetic base stocks are used whenever petroleum (mineral) based oils have reached their performance limit. Synthetic lubricants have improved high temperature characteristics and are more stable over a wide range of operating temperatures.

Additives are extensively used to improve and maintain modern oil performance. Following is a brief discussion of the additives found in reputable brands of engine oil:

Viscosity Modifiers (also called viscosity index improvers) are used to produce multigrade engine oils. They reduce the tendency of the oil to thicken with decreasing temperature and also resist thinning out at elevated temperatures. Viscosity modifiers (VM’s) are not used in monograde engine oils and if the oil in the above example was a monograde, the 8% VM would simply be replaced by base oil.

Detergents operate on high-temperature surfaces, such as the piston-ring area and the piston under-crown, to prevent the formation of harmful deposits on these surfaces.

Dispersants help to keep internal engine surfaces clean by finely suspending contaminants in the oil until they can be safely removed at the next oil change.

Antiwear Agents protect metal surfaces against wear when the lubricating film breaks down. Zinc dialkyl- dithiophosphate (ZDDP) is a long-used favourite to reduce friction between metal surfaces. Some oils also contain friction modifiers to reduce friction even further but their effectiveness tends to diminish during the life of the oil.

Antioxidants inhibit oxidation of the oil.  Oxidation results from exposure of the lubricant to oxygen at high temperatures. The results of such exposure accelerate aging of the oil contributing to oil thickening, sludge and deposits. Antioxidants therefore also help to keep engines running clean.

Rust and Corrosion Inhibitors coat metal surfaces inside the engine to provide a protective film, preventing moisture, oxygen and acids from reaching the metal and causing rust and corrosion.

Pour Point Depressants (PPD’s) provide good oil flow at low temperatures. Oil contains wax particles that can congeal and reduce flow when cooled down. PPD’s modify wax crystal growth at low temperatures and oil continues to flow smoothly.

Foam Inhibitors do not prevent air from mixing with the oil.  Foam inhibitors weaken the surface tension of the air bubbles that are formed allowing them to ‘burst’ more readily and thereby reducing foam.

Another critical characteristic of engine oil is its ability to neutralize acids that are formed during combustion of the fuel. The Total Base Number (TBN) measures the ability of engine oil to neutralize these acids. Detergent and dispersant additives (detergents in particular) are highly alkaline by nature and contribute to the neutralization of acids by proving the engine oil with an alkalinity reserve (TBN).

Although additive technology has improved significantly over the years, the ever increasing stress placed on the oil by modern engines demands that the oil still has to be changed at regular intervals as prescribed by engine manufacturers. Reasons for changing the oil are as follows:

  • To drain contaminants out of the engine when the used oil is replaced. Contaminants include dirt and dust, unburned fuel, combustion byproducts, water/coolant, wear metals and cross-contamination with other lubricants.
  • Additives are consumed during the service life of the oil in the engine and may get depleted.

Then why not simply put more additives into the oil? You can’t necessarily improve the oil’s performance by increasing the additive concentration. In fact, you can make things worse. Engine oils are carefully designed and finely balanced lubrication packages that are scientifically formulated and rigorously tested before they are released in the market. By upsetting this delicate balance you will produce different results than those originally intended.  This raises another issue…supplemental oil additives.

On their own the original additives in modern engine oil are extremely effective but they can become harmful if used in combination with aftermarket or over-the-counter oil additives.  It is therefore no surprise that engine manufacturers do not approve the use of supplemental oil additives. When using a properly formulated motor oil you do not need any additional additives whatsoever. In fact, the additives you may put in can react negatively with the additives the oil company has carefully blended into the engine oil and may result in engine damage and even engine failure.

Automotive Gear Lubricant Viscosity Classification OilChat#4

The SAE J306 standard specifies viscosity limits for the classification of automotive gear lubricants. SAE J306 viscosity grades should not be confused with the SAE J300 viscosity grading system for engine oils (please refer to OilChat #3).

SAE J306 is intended for use by equipment manufacturers when defining and recommending automotive gear, axle and manual transmission lubricants and for oil marketers when labelling such lubricants with respect to their viscosity. It is also used in Owners’ Manuals to advise operators which viscosity grade to use.

The SAE J306 classification is based on the lubricant viscosity at both high and low temperatures. The high temperature kinematic viscosity values are reported in centistokes (cSt). The low temperature viscosities are determined at sub-zero temperatures and are reported in centipoise (cP). High temperature viscosity is related to the hydrodynamic lubrication characteristics of the oil and test results must meet the 100°C viscosity limits listed in the table below.

Low temperature viscosity requirements are associated with the ability of the fluid to flow and to provide adequate lubrication to critical parts under low ambient temperature conditions. The 150 000 cP viscosity value used to define low-temperature properties is based on a series of tests in a specific rear axle design. These tests have shown that pinion bearing failure has occurred at viscosities higher than 150 000 cP in the test axle. The Brookfield test method is used since it provides adequate precision at this viscosity level.

For many years the SAE J306 standard comprised four low temperature grades (SAE 70W, 75W, 80W & 85W) and three high temperature grades (SAE 90, 140 & 250). During 1998 the standard was revised to incorporate two additional viscosity grade designations, SAE 80 and SAE 85. These new grades were included to specify the viscometrics for manual transmission lubricants. Another two viscosity grades were added to the viscosity classification as part of the January 2005 update.

These new grades are SAE 110 (100 °C viscosity between 18.5 and 24.0 cSt) and SAE 190 (100 °C viscosity between 32.5 and 41.0 cSt). The need for these two grades were necessitated  by the wide variation in kinematic viscosity possible within prior versions of J306 for the SAE 90 grade (100 °C viscosity between 13.5 and 24.0 cSt) and the SAE 140 grade (100 °C viscosity between 24.0 and 41.0 cSt). The effect of such wide ranges of kinematic viscosities could result in an axle being serviced with a lubricant that had a viscosity significantly lower or higher than the lubricant that the axle had been designed for, even if the same viscosity grade had been used. Prior to 2005 OEMs may also have been forced to specify a higher viscosity grade than what they actually required, because the wide range of kinematic viscosities of the next lower grade could result in customers using a lubricant with a too low kinematic viscosity.

The current J306 Viscosity Classification for Automotive Gear Oils is:

 

 

 

 

 

 

 

 

 

 

To classify the viscosity grade of automotive gear oils, a lubricant may use one W grade numerical designation, one non-W grade numerical designation, or one W grade in combination with one non-W grade. In all cases the numerical designation must be preceded by the letters “SAE”. In addition, when both a W grade and a non-W grade are listed, the W grade is always recorded first (i.e. SAE 80W-90).

A lubricant which meets the requirements of both a low-temperature and a high-temperature grade is commonly known as a multiviscosity-grade oil. For example, an SAE 80W-90 lubricant must meet the low-temperature requirements for SAE 80W and the high-temperature requirements for SAE 90. Since the W grade is defined on the basis of maximum temperature for a Brookfield viscosity of 150 000 cP and minimum kinematic viscosity at 100 °C, it is possible for a lubricant to satisfy the requirements of more than one W grade. In labelling a W grade or a multiviscosity grade lubricant, only the lowest W grade conformed to may be mentioned on the label. Thus a lubricant meeting the requirements of both SAE 75W and SAE 85W as well as SAE 90 would be labelled as SAE 75W-90, and not SAE 75W-85W-90.

Similar to the SAE J300 grading system for engine oils, the SAE J306 standard only specifies viscosity limits for automotive gear lubricants. Other lubricant characteristics such as performance level and service classification are not considered. These will be discussed in future issues of OilChat.

SAE Viscocity grades for engine oils OilChat#3

The earliest attempts to classify motor oils were made when automobiles first appeared. Even at this early stage, viscosity was recognized as one of the most important characteristics of oil. For this reason the Society of Automotive Engineers (SAE), in co-operation with engine manufacturers, developed the original SAE BOO viscosity grading system for engine oils way back in 1911.

Oils were assigned numbers based on viscosities at certain temperatures. Over the years these standards were updated several times to keep in pace with engine developments and technology advancements.

It has been recognized that oil viscosity at colder temperatures, as well as at high operating temperatures, is very important in the performance of an engine. The SAE has therefore devised two separate viscosity measurement systems, one at a high temperature (100°C) and one at very low temperatures. A rotating viscometer, called a cold cranking simulator, is used to measure viscosities at temperatures as low as -35°C. Because the viscosities are measured in two different temperature ranges, the results are reported in two different units.

The first unit is the centipoise (cP). It is used to  report  the  absolute  viscosity  of  motor  oil  at  low temperatures. This number indicates the ease with which the oil can flow when cold. The other unit is the Centistoke (cSt) which is used to report the kinematic viscosity of motor oil at higher temperatures.

Oils that are suitable for use in colder temperatures are identified by the letter “W” when indicating the SAE viscosity grade. These oil grades must meet maximum viscosity limits at specified sub-zero temperatures and must also meet maximum requirements for the borderline pumping temperatures at very low temperatures. Oils that are suitable for use at higher temperatures have viscosities within specified ranges at 100°C. The standards below have been used to classify engine oil viscosities for a number of years:

SAE BOO Engine Oil Viscosity Grades

If we draw graphs of typical SAE SW and SAE LiO monograde oils with viscosity plotted as a logarithmic function on the vertical axis against temperature as a linear function on the horizontal axis, we will end up with the two solid red lines in the diagram below:

The SAE SW oil will flow sufficiently at low temperatures to protect engines during startup on cold mornings but will be too thin to provide adequate protection at operating temperatures. The SAE LiO oil on the other hand will perform satisfactorily at operating temperatures but will be too viscous to flow sufficiently during startup on cold mornings. The solution? An oil that is ‘thin’ on cold mornings but with a viscosity similar to that of a SAE LiO at operating temperature. But how do we achieve that? With a viscosity modifier (viscosity index improver).

A viscosity modifier (VM) is an oil additive that is sensitive to temperature. At low temperatures, the VM contracts and does not impact the oil viscosity. At elevated temperatures, it expands and an increase in viscosity occurs. If we use a thin oil (let’s say the SAE SW above) as base and add sufficient VM to meet SAE LiO viscosity limits at 1oo·c, we end up with a SAE SW-LiO multigrade oil – the red dotted line. Similarly there are SAE 1 SW-LiO, SAE

20W-SO, etc. multigrade engine oils available in the market. Multigrade oils provide better engine protection at low and high temperatures than monograde 0·11s because they maintain optimum viscosity over the full engine operating temperature range.

Of particular interest is the inclusion of three new high temperature viscosity grades in the latest revision of the SAE BOO Engine Oil Viscosity Classification Standard. They are SAE 16, SAE 12 and SAE 8 (not shown in the table above). These new grades reflect the continued industry push for lower viscosity engine oils to achieve improved fuel economy. They establish specifications to standardize new lower viscosity lubricants such as SAE SW-12, or even SAE OW-8, in the marketplace.

Viscosity and Viscosity Index – OilChat#2

Viscosity is probably the single most important property of oil in terms of lubrication but what is viscosity really? Informally viscosity is the “thickness” of a liquid. For example, if you pour water into a container with a hole at the bottom, the container drains quickly.

However, if you fill the same container with honey, you will find the container drains very
slowly. That is because the viscosity of honey is high compared to that of water. We can
therefore say that viscosity is an indication of a fluid’s resistance to flow.

More formally, viscosity is a measure of the internal friction of a moving fluid. Most liquids are both cohesive and adhesive. Cohesiveness is the intermolecular attraction by which the molecules of the fluid are held together and result in internal friction. A fluid with high viscosity resists motion because its molecular makeup renders it a lot of internal friction. A fluid with low viscosity flows easily because its chemical structure results in very little friction when the oil molecules are in motion.

Imagine you have two horizontal plates or metal surfaces with oil in-between. The oil will cling to the two surfaces because it is adhesive. If the top plate moves horizontally relative to the stationary bottom plate the speed of the oil molecules in between will vary from zero at the bottom to the same speed as the top plate. As the oil layers slip over each other they create friction as a result of the cohesiveness of the oil molecules.

The most commonly used unit for measuring viscosity is the Centistoke(cSt). Viscosity is frequently measured using a device called a capillary viscometer – a U-shaped, graduated glass tube with a capillary of known diameter in the one arm. This method measures the time taken for a defined quantity of fluid to flow through the capillary. When two fluids of
equal volume are placed in the same viscometer and allowed to flow under the influence of gravity, a viscous fluid takes longer than a less viscous fluid to flow through the capillary and a higher viscosity is recorded. Since this method uses gravity as the driving force; the result is kinematic viscosity. The metric unit of kinematic viscosity is mm2
/s (1cSt = mm2/s).

One disadvantage of the capillary viscometer is that the capillary is too small for highly viscous liquids. From everyday experience, it is common knowledge that viscosity varies with temperature. Honey flows more readily when heated. Likewise oils thicken noticeably on cold days with a resultant increase in viscosity. Since viscosity is so dependent on temperature, it should NEVER be quoted without reference to the temperature at which it was measured. Kinematic viscosity is generally measured at li0°C and 1oo·c.

The low-temperature characteristics of certain lubricants are important to their properoperation. Measurement of the sub-zero viscosity of automatic transmission fluids, engine oils, etc. is often used to specify their suitability for service. To measure the viscosity of oils at low temperature, dynamic (or absolute) viscosity is often employedusing a Brookfield viscometer.

Brookfield viscometers rotate a spindle (at a defined speed) in the viscous cold oil and measure the torque required to rotate the spindle in the oil and report viscosity values using the centipoise (cP) or milliPascal-second (Another key property of lubricating oil is Viscosity Index (VI). It is an arbitrary measuring scale (without units) that indicates the change in oil viscosity with change in temperature.

The lower the VI, the greater the change in viscosity of the oil with change in temperature. For example honey is thick at room temperature but when you heat it to say 60°C, it flows readily because the viscosity is reduced significantly and thus has a low VI. However there is hardly any visible change in the viscosity of water from room temperature to 60°C and we can therefore say water has a high VI compared to honey. Failure to use an oil with the proper VI when temperature extremes are expected may result in poor lubrication and equipment failure.

And finally oil viscosity selection. When choosing an oil for a specific application the first
consideration should always be an oil with a viscosity that is sufficient to keep the metal surfaces apart. Unfortunately viscosity cannot be considered in isolation. Selection of the correct viscosity will depend on the temperature, load and speed encountered in a specific application.

Temperature: For machines operating under constant load, constant speed and constant ambient temperature, such as an industrial gearbox in a factory, the ideal viscosity very often results in the lowest stabilized oil temperature. Oils of lower or higher viscosities (than the optimum viscosity) will typically increase the oil’s stabilized temperature due to either drag/churning losses (too much viscosity) or mechanical friction (too little viscosity). If conditions are not constant (variable loads, changing speeds, extreme temperatures, etc.), then there is a need for not only the optimum viscosity but also a high viscosity index to stabilize the optimum viscosity. The wider the temperature range,the greater the need for higher VI oils.

Load: Operating conditions determine the load on machinery. The load on an engine in a vehicle under acceleration or going uphill is higher than that of a vehicle cruising down the highway. Load refers to the pressure on the moving surfaces. Effective lubrication means being able to separate the load carrying surfaces and, if the load changes, then the optimum viscosity of the oil required to separate the surfaces can change. If the load is too high, the oil film may be squeezed too thin to protect the metal surfaces from making contact. This will result in solid friction, meaning an increase in heat, wear and ultimately machine failure.

Speed: The faster a machine operates the stronger the oil film will become as more oil is dragged into the area between the metal surfaces. Therefore, for high speed applications, a low viscosity oil is required. Conversely, forlow speed applications, a high viscosity oil needed to maintain a solid oil film and separate moving surfaces.

In summary, oil viscosity must be sufficient to keep metal surfaces apart yet it must not be so viscous that it will increase drag and waste energy.