With winter approaching it is now an apt time to discuss the Pour Point of lubricants. The pour point of a lubricating oil can be described as the lowest temperature at which the lubricant will flow under specified laboratory conditions. It is often believed that the pour point of a lubricant is the lowest ambient temperature at which the lubricant can be used in a machine, but this is a fallacy.

At best an oil operating at an ambient temperature that is the same as the pour point of the oil, will merely churn at the oil pump until the churning causes an increase in the temperature of the oil. The increased temperature allows the oil’s viscosity to thin down sufficiently so that it slowly begins to flow through the oil passages to the lubricated components. This can take several minutes during which severe damage may be caused to various components due to oil starvation.

Most lubricating oils are still manufactured using paraffinic mineral base oil stocks. Virtually all these mineral base oils contain small amounts of dissolved wax. As the oil is cooled down, the wax begins to separate as crystals. When cooled down further, the wax crystals start to interlock to form a three-dimensional structure that traps the oil in small pockets within the wax structure. When this wax crystal structure becomes sufficiently rigid at low temperatures, the oil will no longer flow. ASTM D97 is the most frequently used test method to determine the pour point of petroleum product. To improve (reduce) the pour point of these oils, pour point depressants (PPDs) are added. PPDs do not in any way affect the temperature at which wax crystallizes or the amount of wax that precipitates. They simply ‘coat’ the wax crystals preventing them to interlock and forming three-dimensional structures that inhibit oil flow. Good PPDs can lower the pour point by as much as 40 ⁰ C, depending on the molecular weight of the oil.

While the pour point of most oils is related to the crystallization of wax, certain oils, which are essentially wax free, such as polyalphaolefins (POAs), have viscosity-limited pour points. With these oils the viscosity becomes progressively higher as the temperature is lowered until no flow can be observed. The pour points of these oils cannot be lowered with PPDs. However, due to PAOs’ unique nature, they provide excellent low-temperature viscometrics and very low pour points that cannot be achieved by adding PPDs to mineral oil.

Just as important as pour point (if not more) is Cloud Point. The cloud point of an oil is the temperature at which a cloud of wax crystals start to appear when a sample is cooled under prescribed conditions. Below this temperature, the viscosity of the oil increases exponentially with decreasing temperature. This may well lead to oil pump cavitation in oil circulating systems, even before the pour point of the oil is reached — particularly in systems where the oil pump is positioned higher than the oil reservoir. ASTM D2500 is the most commonly used test method to determine the cloud point of petroleum products.

Considering all the above a good rule of thumb is that the pour point of a lubricating oil should be at least 10^OC below the lowest anticipated ambient temperature. This will ensure dependable lubrication and better equipment reliability in the long term.

The regimes of lubrication can be compared to water skiing. Skiers normally start by entering the water with their skis on and holding onto the ski rope. When the skier is ready, the boat starts and the skis begin to move on the sand (boundary lubrication). As the boat accelerates, contact between the skis and sand is reduced (mixed lubrication). When the speed is sufficient, the skier rises out of the water with the front of the skis also out of the water and pointing upwards at an angle. It is this wedge profile between the skis and water that allows the skier to hydroplane on the water (hydrodynamic lubrication).

Before addressing lubrication regimes, we need to look at how friction and wear occur between moving machine surfaces. These surfaces appear smooth to the naked eye, but they are actually rough and uneven. Tiny peaks called asperities stick out and scrape against asperities on the opposing surface, causing friction and wear. The prime function of a lubricant is to prevent, or at least reduce, wear between surfaces moving on one another. We will endeavour to explain the lubrication of a plain journal bearing in parallel to the skiing analogy above. To enable the shaft to rotate in the bearing on the left, the diameter of the shaft must be less than the inside diameter of the bearing. This creates a wedge similar to the one between the skis and the water.

Boundary Lubrication is associated with metal-to-metal contact between moving surfaces.

 During start-up, the shaft and bearing asperities in a lubricated system will be in physical contact. The major portion of wear in any machine takes place in this regime. To prevent excessive wear within this regime, lubricants are formulated with additives to form a low-friction, protective layer on the wear surfaces. The base oil of the lubricant acts as a carrier to deposit the additives where they are needed. A suitable viscosity is important to ensure the oil can flow into tight spaces to lubricate the surfaces. The additive chemistry (anti-wear or extreme pressure) used within the lubricant is determined by the application.

Mixed lubrication is a transitional regime between the boundary and hydrodynamic lubrication, sharing characteristics of both. Oil molecules are cohesive as well as adhesive and cling to the shaft. As the shaft gains rotational speed, oil is carried into the wedge and starts to lift the shaft, but not sufficiently to separate the two surfaces completely. Mixed lubrication can also occur between surfaces where high loads are encountered, such as when reciprocating pistons slide against cylinder walls. With mixed lubrication, wear protection depends on both the lubricant viscosity, as well as the additives within the oil formulation. A lubricant with a too low viscosity will result in excessive metal-to-metal contact between the shaft and bearing.

Hydrodynamic lubrication (also known as full film lubrication) occurs when speed and load are such that the oil wedge between the shaft and bearing separates the surfaces completely. This is the ideal condition to avoid friction and wear. In fact, as long as this condition exists, no anti-wear or extreme pressure additives are required, and friction is so low that bearings can operate indefinitely without wear. Any friction remaining comes from the cohesiveness of the oil molecules as they slide past each other during operation. A lubricant with too high viscosity will result in an increase in the oil’s molecular friction. This will in turn increase operational temperatures and energy loss.

The lubrication regimes discussed above pertain to surfaces sliding against each other, such as journal bearings, reciprocating pistons, gears, thrust bearings, chains and guide bearings. In addition to this there is yet another lubrication regime:

Elastohydrodynamic lubrication is the condition that occurs when a lubricant is introduced between surfaces that are in rolling contact, such as roller bearings.

As the oil enters the contact zone between the roller and raceway (by rolling action), the pressure that develops is sufficient to separate the roller and raceway completely. In fact, the pressure is high enough for the surfaces to deform elastically. The deformation only occurs in the contact zone, and the metal elastically returns to its normal form as the rotation continues, hence the term elastohydrodynamic lubrication. This lubrication regime may be compared to a car tyre aquaplaning on water. It occurs when water on the road accumulates in front of the tyre faster than the weight of the car can push push it out of the way.

The curve below shows the transition of the lubricating conditions between sliding surfaces. The vertical axis represents the coefficient of friction (an indication of the amount of friction) between sliding surfaces. The horizontal axis is a function of the relative speed between the two surfaces:

The curve clearly illustrates that the coefficient of friction is the highest when speeds are low and boundary conditions prevail.  Anti-wear and extreme pressure additives play an important role in this regime. The coefficient of friction is reduced dramatically as speed is increased in the mixed lubrication regime. Once hydrodynamic lubrication is reached, the coefficient of friction is at its minimum. This is because there is no longer any physical contact between the two surfaces owing to the fluid film carrying the entire load. The remaining frictional force is due to the internal friction of the fluid (we mentioned earlier oil molecules are cohesive). When the sliding speed increases further, the coefficient of friction rises again owing to drag (increase in viscous resistance). If the equipment constantly operates in this condition, the viscosity of the oil being used should be reduced. it is therefore evident that oil viscosity is important in the hydrodynamic regime.

Please be aware that the above is a simplified explanation of lubrication regimes and it does not address factors such as Newtonian behaviour, pressure vector distribution, position of shaft in the bearing during the different regimes and bearing parameters.

This blog continues on from Blog 18 where we looked at compressor lubrication…

The lubrication requirements of positive displacement compressors are in many instances the most demanding of all compressor types. Regardless of size and configuration, all reciprocating compressors have similar components to be lubricated. These are pistons, piston rings, cylinder walls, valves, crankcase bearings and cross head components (if fitted).

It is particularly important that reciprocating compressor oils should provide adequate protection against wear and deposit formation. The piston ring and cylinder contact area experience all the different lubrication regimes (i.e. boundary, mixed, and hydrodynamic) during every stroke of the piston.

Boundary lubrication conditions occur near the top and bottom dead centre when the piston slows down to change direction of travel. This requires some form of anti-wear protection. Exposure of the lubricating oil to hot oxidizing conditions can be severe in reciprocating compressors. Some oil oxidation is inevitable, particularly in the discharge valve area. Adherence of oxidized residues to hot valve surfaces can be minimized by including a stable detergent/dispersant in the lubricating oil.

An ideal lubricating oil for reciprocating air compressors would be made from a well-refined stable base oil with ashless anti-wear additives and good high temperature detergents/dispersants, along with oxidation inhibitors, foam suppressants and rust inhibitors for protection during shutdown. Viscosity requirements of reciprocating compressors are in the ISO viscosity range 68 to 220, or even higher for very high pressure, high temperature machine.

These positive displacement compressors use two intermeshing screw-shaped rotors for compression. The two major sub-categories are wet and dry screws. Dry screw designs have timing gears to synchronize the screw movement. However, the most common type of screw compressor is the flooded or wet screw design where the primary (male) rotor drives the secondary (female) rotor.

Rotary Screw Compressors

In oil-flooded screw compressors the lubricant is injected into the air being compressed. The oil provides a lubricating and sealing film between the two screws. With these compressors the air and oil must be separated after compression. The major functions of the lubricant are to cool, seal, prevent rust and lubricate the bearings, rotors and shaft seals. In oil-flooded screw compressors there is intimate contact between the air and the lubricant, causing great potential for oxidation and deposits.

The lubrication requirements of these compressors are similar to that of reciprocating compressors, except that the anti-wear requirements of screw compressors are not quite as demanding as reciprocating compressors. Viscosity requirements of screw compressors are in the ISO viscosity 32, 46, 68 or 100 range. Oil-flooded screw compressors are the main compressor type used for air compression in industrial applications.

Rotary Vane Compressors

Rotary (sliding) vane compressors consist of a rotor with a number of blades (vanes) in slots in the rotor. The rotor is mounted offset in its housing. Centrifugal forces ensure that the vanes are always in close contact with the housing. These compressors are available in oil-lubricated or oil-less designs. The type depends on the application, duty-cycle, and maintenance preferences.

With non-lubricated variants, you replace the vanes with every service. When servicing oil-lubricated rotary vane compressors you replace the oil, filter and maybe the oil separator. Lubrication requirements of oil-lubricated rotary vane compressors are similar to those of oil-flooded (wet) rotary screw compressors. Oil is injected into the air (flooded lubrication) to cool, seal and lubricate the vanes, bearings and endplates. Obviously, an oxidation inhibited oil is required.

Contact of oil with the air suggests that a foam inhibitor would be beneficial. A rust inhibitor will provide protection against rusting during shutdown and for intermittent operation. In addition, the oil should have good detergent/dispersant properties to maintain a deposit-free circulating system and prevent vane sticking. The vanes may make contact with the cylinder walls in a boundary lubrication condition; therefore, anti-wear oils are often used, ranging in viscosity from ISO 46 to 50, depending on the application.

Dynamic Compressors

Radial Centrifugal and Axial Flow compressors use very high-speed spinning blades or impellers to compress the air. These compressors do not require internal lubrication, hence only rust and oxidation inhibited oils are commonly used to lubricate and cool the outboard bearings. Due to the high speed, relatively low viscosity oils are used. The lubricant generally recommended for dynamic compressors is highly refined rust and oxidation inhibited oil of ISO 32 viscosity grade. Where a gear driven speed increaser is used, an ISO 46 or even ISO 68 viscosity grade may be required.

The same types of compressors that are used for air are also used for gases. Hydrocarbon based lubricants, mineral and synthetic (PAO), should NEVER be used for compressing active gases such as hydrogen, chloride, oxygen, etc. These gases may react chemically with hydrocarbon oils. Under pressure the chemical mixtures of these gases and hydrocarbon oil can be explosive. Lubricants blended with Group V base oils, normally polyalkylene glycol, should be used for gas compressors.

The choice of a compressor lubricant depends on the type and construction of the compressor, the gas being compressed, the degree of compression and the final outlet temperature. Most compressor manufacturers recommend lubricants that have been tested in their machines under controlled conditions. Make sure you are familiar with your manufacturers’ recommended lubricants, keep them in stock and adhere to the specified service intervals.

If you are in doubt our experts are at your disposal and ready to provide you with advice and answer any questions you may have. For more information, call 011 462 1829.

 

A compressor can be described as a pump or other device that ‘inhales’ air and delivers it at a higher pressure. Compressors are also used to compress a variety of gases. The very first air compressor was the human lung. To illustrate, we use compressed air from our lungs to inflate balloons. In the early days of mankind our ancestors used their breath to stoke fires and to increase the temperature of glowing coals.

With the advent of the Metal Age more heat was required to melt metals, such as gold and copper, and circa 1 500 B.C. a basic type of air compressor, called bellows, was invented. This device was a hand-held, and later foot-operated, flexible bag made of animal skin, that produced a concentrated blast of air that was ideal for achieving higher temperature fires. In 1 762 during the early days of the Industrial Revolution John Smeaton, an innovative engineer, designed an air blowing cylinder driven by a water wheel. It soon replaced the bellows in many industrial applications.

Today compressors are generally driven by electric motors, turbines or internal combustion engines. Modern compressors come in many designs and sizes, ranging from small units at petrol stations to inflate car tyres, to massive industrial machines that are too large to fit into an average-sized garage. The air pressure in car tyres is usually between 2 and 3 bar (29.0 and 43.5 pounds per square inch). The latest high-performance compressors can deliver pressures well in excess of 70 bar (more than 1000 psi).

Lubrication plays a critical role in the efficient and reliable operation of compressors. However, before we look at compressor lubrication, we need to understand the design and operation of the most common types of compressors available on the market. Compressors are divided into two main categories: Positive Displacement and Dynamic Compressors. Following is a brief discussion of the most popular compressors within these categories:

Positive Displacement Compressors

These compressors work by filling a chamber with air. The volume of the chamber is then reduced and consequently, the pressure in the chamber is increased. By nature of their design, Positive Displacement Compressors can deliver very high pressures. The most common Positive Displacement Compressors are:

Reciprocating Piston

Reciprocating compressors function similarly to a car engine. A piston slides back and forth in a cylinder, which draws in and compresses the air, and then discharges it at a higher pressure. Reciprocating compressors are frequently multiple-stage systems, which means that one cylinder’s discharge will lead into the input side of the next cylinder. This allows for more compression than a single stage. Due to their relatively low cost, reciprocating compressors are probably the most commonly used compressors.

Rotary Screw

 These compressors use two meshing screws (also called rotors) to compress the air. In oil flooded rotary screw compressors, lubricating oil bridges the space between the rotors. This provides a hydraulic seal and transfers mechanical energy between the driving rotor and the driven rotor. Air enters at the suction side, the meshing rotors force it through the compressor, and the compressed air exits at the end of the screws.

Rotary Sliding Vane

 Rotary vane compressors consist of a rotor with a number of blades (vanes) inserted in radial slots in the rotor. The rotor is mounted offset in a housing. As the rotor turns, the blades slide in and out of the slots, keeping contact with the wall of the housing. Thus, a series of increasing and decreasing volumes are created by the rotating blades to compress the air. Centrifugal forces ensure that the vanes are always in close contact with the housing to form an effective seal.

Dynamic Compressors

Dynamic compressors use very high speed (up to 60,000 rpm) spinning blades or impellers to accelerate the air. The increased velocity causes an increase in air pressure. Dynamic Compressors deliver large volumes of air but generally at lower pressures. The following designs are the most common types of Dynamic Compressors:

Radial Centrifugal

 A rotating impeller in a shaped housing is used to force the air to the rim of the impeller, increasing the velocity of the air. A diffuser (divergent duct) section converts the velocity energy to pressure energy. Radial compressors are primarily used to compress air and gasses in stationary industrial applications.

These compressors use fanlike airfoils (also known as blades or vanes) to compress air or gas. The airfoils are set in rows, usually as pairs, one rotating and one stationary. The rotating airfoils (rotors) accelerate the air. The stationary airfoils (stators) redirect the flow direction, preparing it for the rotor blades of the next stage. Axial compressors are normally used where very high flow rates are required. By nature of their design, axial flow compressors are almost always multi-stage.

The majority of compressors requires some form of lubrication to either cool, seal or minimize wear of their internal components. Many compressors are adequately lubricated by premium-grade turbine oils. We will address the specific lubrication requirements of the above compressors in more detail in our next blog, Blog 19.

 

Hydraulic brake fluid plays a crucial role in the performance and safety of mountain bikes. Specially designed for hydraulic braking systems, this fluid serves as a medium to transmit force from the brake lever to the brake caliper. Known for its excellent thermal stability and resistance to compression, hydraulic brake fluid ensures consistent and reliable braking even under extreme conditions. Its low viscosity allows for efficient transfer of hydraulic pressure, resulting in quick and responsive braking. Furthermore, hydraulic brake fluids are formulated to prevent corrosion and maintain the integrity of brake components. Regular maintenance, including fluid checks and replacement, is essential for optimal brake function and rider safety.

Blue Chip Brakz is a high-performance fluid especially designed for use in hydraulic brake systems fitted to modern mountain bikes. Due to its special formulation Blue Chip Brakz is suitable for all cycle brake systems that require mineral or synthetic based brake fluids. It is available in handy 125ml plastic sachets.

Order online here: https://www.bcl.co.za/shop/ or contact us on +27 11 462-1829 / internalsales@bcl.co.za.

 

Q8 Formula Special G Long Life 5W-30 is a new generation synthetic engine oil designed for use in modern, high performance petrol engines and light commercial diesel engines. It is formulated with the latest mid-SAPS additive technology to exceed ACEA C3 and API SN/CF requirements and to comply with the stringent requirements of major engine manufacturers.

Q8 Formula Special G Long Life 5W-30 is a high-performance engine oil formulated for a wide variety of European, Asian and American engines, including BMW, Hyundai, MB, Toyota, VW/Audi and many more. It delivers superior protection against engine wear, high temperature deposits and sludge formation, resulting in outstanding engine cleanliness and increased engine durability. Formula Special G Long Life is suitable for extended drain intervals and is compatible with exhaust after-treatment systems, such as exhaust catalysts and diesel particulate filters. It is recommended for passenger cars and light commercial vehicles with normally aspirated or turbocharged engines.

Car manufacturers have been recommending SAE 5W-30 engine oils for new vehicles available on the South African market for some time now. When these vehicles are under warranty their owners have little option but to use the motor oil supplied by the agents, but many of these vehicles are now out of warranty. The manufacturers’ oils come with exorbitant prices hence we are getting more frequent requests for more affordable SAE 5W-30 motor oils. Good news is that Q8 Formula Special G Long Life 5W-30 is available at very competitive prices, certainly much lower than what vehicle owners would be charged by the manufacturers’ agents.  

Q8 Formula Special G Long Life 5W-30 also addresses the justified concerns of many motorists that SAE 5W-30 oils are ‘too light’ for the harsh South African operating conditions and extreme temperatures. The high viscosity index and shear stable synthetic formulation of Special G Long Life render it suitable for the most severe applications.

We trust you will share in our excitement at delivering this superb product to the South African market. For further information about Q8 Formula Special G Long Life 5W-30 simply contact your local representative, phone 011 462 1829 or email us at info@bcl.co.za. 

An engine is assembled from many individual parts. Ensuring a good oil flow to critical areas is essential to guarantee the efficient and trouble-free operation of the engine. By lubricating an engine with the right engine oil, you can achieve smoother operation and better engine durability, saving you maintenance and fuel costs.

All engines, whether for heavy-duty vehicles or passenger cars, have critical engine parts that must be properly lubricated to avoid premature engine wear, operational problems, and catastrophic failures. In this article, we will address these critical engine components and explain how to protect them.

1. Turbocharger

A turbocharger increases the engine’s efficiency and power output by forcing extra air into the combustion chamber. Operating at high speeds of up to 250,000 rpm, a turbocharger generates excessive heat.

Risks of Turbocharger Failure

With peak temperatures of up to 1000°C, the turbocharger creates a harsh environment for engine oils. These high temperatures increase the formation of deposits in the oil, resulting in a gradual loss of power and efficiency and, eventually, severe turbocharger failures.

The Importance of Choosing the Right Lubricant

To ensure the smooth operation of the turbocharger, the engine oil must excel in cleanliness control and oxidation control to manage deposits at high temperatures. Using a high-quality lubricant helps maintain power and efficiency throughout the oil drain interval.

2. Piston and Liners

The engine block consists of cylinder liners, pistons, and rings. Together, they generate the combustion pressure that allows for efficient power generation. To ensure efficient combustion and maximum engine efficiency, it is crucial to prevent wear and control deposit formation in the lubricant.

Risks of Piston and Liners Failure

The formation of piston deposits can cause piston ring sticking, leading to damage to cylinder liners, pistons, and rings. This results in a loss of combustion pressure and excessive blow-by, further exacerbating oxidation and cleanliness problems.

The Importance of Choosing the Right Lubricant

A high-quality engine lubricant controls piston deposit formation and prevents wear on cylinder liners, pistons, and rings. It helps maintain optimal compression and engine power, ensuring engine durability.

3. Crankcase

The crankcase protects several key engine parts, such as the crankshaft and connecting rods, from external objects. A collection of capillary oil feeds allows for dedicated lubricant delivery to various components.

Risks of Crankcase Failure

The formation of soot and sludge can clog capillary oil feeds, resulting in crucial component failure. It also obstructs the removal of contaminants during maintenance service, leading to further wear and durability issues.

The Importance of Choosing the Right Lubricant

A lubricant that effectively controls sludge and soot ensures clean engines, guaranteeing a good oil flow to important engine components, reducing wear, and improving efficiency.

4. Valve Train

The valve train manages valve operation by controlling the amount of air and exhaust gas flowing into and out of the engine.

Risks of Valve Train Failure

The precise geometry of the cam-operated mechanism is critical for engine operation and can be affected by wear and soot formation. A lubricant with poor wear protection, inadequate soot control, and insufficient valve lubrication can result in excessive wear, reduced valve lift, and potential component failure, such as valve seat wear and related valve recession.

The Importance of Choosing the Right Lubricant

A lubricant with good wear protection and valve lubrication ensures the precise geometry of cams, valves, and valve seats, maintaining the correct air and exhaust gas ratio. As a result, the engine will maintain its power and efficiency.

5. Main and Rod Bearings

Main crankshaft bearings support the crankshaft and enable its rotation. These bearings provide oil flow to the feed holes in the crankshaft. Connecting rod bearings facilitate the rotating motion of the crank pin within the connecting rod. Both main and rod bearings are responsible for efficient lubrication with minimal power loss.

Risks of Bearing Failure

Corrosion of the bearings is a significant risk that can lead to rod and cam bearing damage and potential engine failures. Insufficient lubrication can result in oil leakage, a loss of oil pressure, and expensive component replacement.

The Importance of Choosing the Right Lubricant

A high-quality lubricant prevents corrosion and ensures extended protection of the bearings, leading to less unscheduled maintenance and significant cost savings.

Q8Oils develops all products in close cooperation with Q8 Research, an experienced team of scientists. We consider it extremely important to offer the right lubricant for any application to ensure that customers receive optimal performance and protection for their engines.

When you open a container of lubricating grease, chances are you may see a thin layer of oil at the top of the grease. The first thought that usually jumps to mind is whether the grease is suitable for use. The answer is in most instances, yes, but to understand the phenomenon of oil separation (bleeding) we need to revisit the fundamentals of grease.

Grease is a dispersion of a thickening agent in a liquid lubricant. the thickener can be compared to a ‘sponge’ that soaks up the lubricant. When the grease is subjected to stress or shear movement, the thickener releases the oil to provide the necessary lubrication. This is generally known as Dynamic Bleed. It is important that the grease has a controlled rate of bleeding during use to properly lubricate the bearing or component it has been placed in. The greater the amount of sheer stress encountered, the faster the grease thickener releases the oil. the thickener imparts little, if any, lubrication. If the thickener did not release the oil, the grease would be unable to perform its lubricating function.

In service, grease should also have a fair degree of reversibility after the stresses that have released the oil are relaxed. Reversibility can be described as the ability of the grease to recapture most of the oil and return to its original consistency when the equipment is shut down. The reversibility characteristics of grease are influenced by the type and amount of thickener used. The higher the thickener content, the greater the oil retention. As the base oil content is increased and the amount of thickener decreased, the forces that hold the oil also decrease, resulting in the base oil being loosely held in the thickener and easily separated.

Considering the above, one would think that using a higher thickener content is better. However, as mentioned earlier, grease with a thickener that does not release the oil readily, would be unable to perform its lubricating functions. It is therefore important that grease must have the proper balance of oil and thickener to function properly. The oil on top of grease in a container that has been opened for the first time is called Static Bleed. Static bleed, also referred to as oil puddling, occurs naturally for all types of grease and the rate of bleeding depends on the composition of the grease. Static oil bleeding is affected by:

• Storage Temperature
• Length of period in storage
• Vibrations the container may be exposed to during transport or storage
• Uneven grease surface in the container (the presence of high and low spots)

These conditions can cause weak stresses to be placed on the grease, resulting in the release of small amounts of oil and over time a puddle of oil can form on top of the grease. Reasonable static bleeding does not result in the grease being unsuitable for use. Any oil that has puddled on the grease can be removed by decanting the free oil from the surface or manually stirring it back into the grease. The quantity of oil that has separated from the grease is generally insignificant and represents a mere fraction of the total quantity of oil that is held in the thickener (typically less than 1%). This small amount of oil will not adversely affect the consistency of the remaining product and will have little or no effect on the performance of the grease.

Conclusion

It is therefore safe to say grease with puddling on the top is suitable for use subject to the following conditions:

• The amount of oil should be small, covering only low spots on the surface of the grease.
• The grease must readily absorb the oil upon stirring.

Tractors don’t come up on our radar screens all that often but modern farm equipment is a far cry from the “mechanical plow horses” of yesteryear. These new machines may still not break any speed record, but space technology is now being incorporated into agricultural equipment in the form of GPS devices, onboard computers, auto-steer system and even driverless technology!

Notwithstanding this array of state-of-the-art gizmos, lubrication still plays a critical role in the efficient and reliable operation of agricultural machinery. Tractors and other farm equipment, such as combined harvesters, have various components that need to be lubricated. These include the engine, transmission, final drives, oil immersed ( wet ) brakes hydraulic system and the power take-off ( PTO ). Just imagine the cost consequences if farmers had to stock different oils for all these applications. Furthermore, with so many lubricants in the oil store, there is also the risk of using the wrong oil for a specific component. It is therefore no wonder that agricultural equipment manufacturers and oil companies have worked together to come up with multifunctional lubricants:

Super Tractor Oil Universal (STOU/SUTO)

These oils fulfill several roles and make machine maintenance much simpler. They also reduce the number of lubricants farmers need to keep around because they can generally be used for all the applications mentioned above. When you peruse the product data sheet of a reputable STOU you will find that it meets the requirements of a host of Industry and Equipment Manufacturers’ (OEM) specifications. These may include, but are not limited to, the following:

• Engines: API CG-4/SF
• Gears: AP GL-4
• Transmissions: ZF TE-ML 06A / 06B / 06C / 06G
• Wet Brakes: Case MS 1317
• Hydraulics: Eaton Vickers M-2950-S.

A STOU fluid can be described as a general-purpose farm lubricant with reasonable engine performance, fair load carrying capacity for gears and moderate hydraulic oil performance. However, as engines become more demanding, transmissions more sophisticated and hydraulic system pressures higher, trying to meet all the requirements with one fluid becomes more complicated. For instance, if a manufacturer recommends an API CI-4 performance level oil for the engine, two separate lubricants may have to be used since it is unrealistic to expect a single oil to meet API CI-4 and all the other service categories mentioned above. In such an instance it would be advisable to use a dedicated engine oil and a higher performance multifunctional lubricant for the other components.

Universal Tractor Transmission Oil ( UTTO )

These lubricants are also referred to as Tractor Hydraulic Fluid ( THF ) or Transmission, Differential and Hydraulic ( TDH ) fluid. They are used where the equipment manufacturer recommends a separate engine oil. UTTO shave no engine oil credentials, better hydraulic oil performance and improved wet brake fluid characteristics.

When you compare STOU and UTTO product data sheets you may well find they have some transmission, rear axle, wet brake and hydraulic oil specifications in common. However high-performance UTTOs will boast with OEM specifications that are unlikely to be met by STOUs such as:

• Case MS 1207: Hy-Tran Plus, transmissions, hydraulics, wet brakes
• Massey Ferguson CMS M 1141: Transmissions, hydraulics, highly loaded wet brakes
• Volvo 97302-10: Transmission with built in wet brakes

As tractors become more sophisticated and require higher quality oils for satisfactory performance, there will most likely be an increased trend away from the all-purpose STOU fluid to a specific engine oil and UTTO combination.

TO-4 Fluid

UTTOs should not be confused with TO-4 fluids. UTTOs are mainly used in agricultural applications, although they are sometimes recommended for construction machines, such as Bell ATDs. TO-4 fluid originates from the Caterpillar TO-4 ‘Transmission Oil’ specification. TO-4 has become a standard term used within the industry for a specific type of additive/ fluid. TO-4 fluids normally meet Allison C4and other OEM requirements as well.

Although both UTTOs and TO-4 fluids are designed for wet brake applications, they are not interchangeable since they have different frictional properties.Construction machinery, for which TO-4 fluids are intended, is normally much bigger and heavier than agricultural equipment. A higher level of friction is required to ensure that these heavy machines can stop on steep slopes, such as access roads down open cast mines.Tractor size, and therefore weight, is limited, as they need to use public roads, and therefore less friction is required to stop agricultural equipment. This results in TO-4 fluids having a higher coefficient of friction than UTTOs. Using the wrong fluid will mean that fluid/brake surface interaction will be affected and thereby reducing braking efficiency with possible catastrophic results.

Conclusion

Know your equipment manufacturer’s recommended lubricants, have them on hand and pay attention to tractor and equipment service intervals. If in doubt our experts are at your disposal, ready to provide you with advice and to answer any of your questions.

One of the most frequent questions that comes up around gear oil is “Can GL-5 gear oils be used in vehicles with synchronized manual transmissions?”

Modern high performance automotive gear oils (API GL-4 and GL-5) are formulated with oxidation and rust inhibitors, antifoam agents, pour point improvers and extreme pressure (EP) additives. The most common EP additives are sulfur-phosphorus (S-P) compounds that adhere to metal surfaces through polar attraction.

When subjected to heat and/or pressure (from a collapsing lubricant film) they react chemically with the metal surface to form a tough EP film. In general, the higher the GL rating, the higher the S-P content and the higher the EP protection provided.

Traditionally the engines of motor vehicles were placed in the front with a long driveshaft transmitting power to the wheels at the back – see Figure 1 below. A differential is used to let the power from the driveshaft make a 90 degree turn so it can get to the wheels via the side shafts (axles) – Figure 2. In days gone by vehicles were designed quite high on their wheels and the position of the driveshaft was not an issue. A crown wheel (large gear) and pinion (small gear) are used in the differential to ‘bend’ the power from the driveshaft to the side shafts (Figure 3). In this configuration the axis (center) of the pinion is on the same level as that of the crown wheel.  This design, however, became a problem when the height of vehicles was reduced to make them more streamline, since lots of interior space had to be sacrificed to accommodate the driveshaft tunnel – that hump that runs from the front to the rear in the floor of the vehicle. This problem was reduced with the introduction of hypoid differentials where the axis of the pinion is set below the axis of the crown wheel (Figure 4), resulting in a lower driveshaft.

Generally, a differential with the axis of the pinion on the same level as that of the crown wheel (Fig 3) will be adequately lubricated by an API GL-4 oil although GL-5 will provide better protection.  Today, however, most rear wheel drive vehicles are fitted with hypoid differentials (Fig 4). Because of the increased sliding contact between hypoid gears, their contact pressure is higher and API GL-5 oils are required to lubricate these diffs effectively.

Most API GL-5 oils correctly claim they meet GL-4 requirements but does that make them suitable for synchromesh or synchronized transmissions? The answer is NO! They meet API Gear Oil specifications, not transmission oil requirements. The API GL-4 and GL-5 categories do not mention anything about transmission oil requirements, synchronized transmission in particular.

Synchronized transmissions are fitted with synchronizers to allow light and easy gear shifting and to eliminate that grinding sound, particularly when changing to a lower gear. Synchronizers use friction to match the speed of the components to be engaged during shifting. Slippery lubricants such as GL-5 hypoid gear oils can reduce the friction between the mating synchronizer surfaces and thereby effecting synchronizer operation negatively. In addition, synchronizers are often made of copper alloys. The way in which EP additives work can be disastrous to these ‘soft’ alloys. The S-P may attack the yellow metals chemically, causing synchronizers to fail prematurely.

Another question is why API Category GL-6 is obsolete when it offers protection from gear scoring in excess of that provided by API GL-5 gear oils? To answer this question, we need to take a trip down memory lane.  Many years ago, Ford required improved protection in certain of their pickup trucks and about the same time General Motors introduced a differential with a very high pinion offset.

This necessitated a higher gear oil service category and API GL-6 was developed to provide the greater protection needed. In fact, the GM differential was used in the GL-6 test procedure. This level of protection is still claimed by some oil manufacturers, but can no longer be tested since GM have stopped producing these diffs. A shift to more modest pinion offsets and the obsolescence of API GL-6 test equipment have greatly reduced the commercial use of API GL-6 gear lubricants. Nevertheless, some manufacturers of high performance cars still specify this level of EP performance for their vehicles.

The photo below shows a brass synchronizer that had been damaged to such an extent that it no longer “grips” its mating surface.  API GL-4 lubricants contain about half the S-P additives of their GL-5 counterparts. This means they do not react with synchronizers quite as aggressively but then they provide less wear protection for transmissions. This nonetheless is not a serious problem since there are no hypoid gear arrangements in synchronized transmissions.

What is then used in the transaxles of front wheel drive vehicles where the transmission and differential are combined in one unit? Oil selection is influenced by the transaxle design:

1. Contact surfaces of the gears are big enough to carry the load and less protection is required from the lubricant.
2. Most transaxles are designed without hypoid gears.

Another question is why API Category GL-6 is obsolete when it offers protection from gear scoring in excess of that provided by API GL-5 gear oils? To answer this question, we need to take a trip down memory lane.  Many years ago, Ford required improved protection in certain of their pickup trucks and about the same time General Motors introduced a differential with a very high pinion offset. This necessitated a higher gear oil service category and API GL-6 was developed to provide the greater protection needed. In fact, the GM differential was used in the GL-6 test procedure. This level of protection is still claimed by some oil manufacturers, but can no longer be tested since GM have stopped producing these diffs. A shift to more modest pinion offsets and the obsolescence of API GL-6 test equipment have greatly reduced the commercial use of API GL-6 gear lubricants. Nevertheless, some manufacturers of high-performance cars still specify this level of EP performance for their vehicles.

In addition to API GL specifications, synchronized transmissions and limited slip differentials often have specific frictional requirements and reference should always be made to the equipment manufacturers’ oil recommendations for these units.