It’s a question many vehicle owners ask: Should I flush my engine?

The short answer? Probably not—as long as you’re following a regular oil change schedule using a quality lubricant from a reputable supplier.

Why Engine Flushes Get a Bad Rap

Mention “engine flush” to any seasoned mechanic or technician, and you’re likely to get a worried look. That’s because flushes have a checkered past—stories abound of engine flushes gone wrong, resulting in serious damage. Traditionally, engine flushes were a desperate measure used on severely neglected engines and carried significant risk.

Older flushing methods involved draining some of the oil, adding a chemical additive, running the engine at idle for 10 to 15 minutes, then draining and replacing the oil and filter. These additives—often made with solvents or strong detergents—could damage seals, bearings, turbochargers and other vital components. In some cases, volatile solvents even posed a fire risk.

Manufacturer Warnings

Most vehicle manufacturers have issued technical bulletins warning against crankcase flushes. Not only are they usually unnecessary, they can void your warranty. If you suffer engine failure and your records show a flush was performed, the dealership may reject your warranty claim.

When Sludge Becomes a Problem

It’s true that sludge and varnish can build up in poorly maintained engines. Sludge is a cocktail of oxidised oil, soot, combustion gases, water vapour and other contaminants. But engines that are regularly serviced don’t get this dirty.

Common signs of sludge buildup include:

• Noisy tappets or lifters (a metallic clicking sound)
• Persistently low oil pressure
• Oil warning light that won’t go off
• Slow oil drainage
• Thick, greasy residue on the dipstick or inside the oil filter

You can check for sludge by removing the oil cap and shining a torch into the engine. Clean engines have a glistening metallic appearance. If you see thick, tar-like build-up, sludge may be present.

A Word in Defence of Modern Engine Flushes

Today’s engine flush additives are far gentler than the solvent-heavy products of the past. Some contain advanced detergents that clean more safely. However, the best defence remains a good offence: regular maintenance.

Modern engine oils – like Q8 lubricants – are already formulated with detergents and dispersants that keep your engine clean under normal operating conditions. Even if your engine has missed a few oil changes, high-quality oil will gradually clean it out over successive services.

The Bottom Line

If your engine is maintained properly, a flush simply isn’t needed. Change your oil regularly, use a good-quality oil and filter, and your engine will take care of you for years to come. It’s that simple.