You’ve probably heard it before, but it can’t be stressed enough: oil is the lifeblood of your car. Despite this, most car owners don’t pay it much mind; it’s just something to be checked at the usual 10,000km tune-up. Unfortunately, by the time 10,000km has swung round, your engine’s oil may no longer be doing an adequate job. When this happens, there’s not a component of your engine that won’t be affected.

What does engine oil do?

Without getting bogged down in the nitty-gritty, this is how your car manages to get you from A to B: Expanding combustion gases push a piston, which in turn rotates a crankshaft, and, through a system of gears in the powertrain, rotates the wheels. Basically, your car’s engine is full of moving parts, all of which are touching something else. Science tells us that movement causes friction, which causes heat. Too much heat causes damage, which is why we use oil.

Rub your hands together and you’ll find they get warm very quickly. Put some oil on your hands (or soap) and rub them together, and the heat generated is far less. The lubricating nature of engine oil keeps the engine cool (relatively speaking) and slows down the wear and tear of components as they move against one another.

Why does engine oil need to be replaced?

Engine oil operates in a tough working environment and, over time, becomes diluted and contaminated. On a cold start-up, petrol will actually enter and mix with the engine oil, thinning it out and inhibiting its ability to lubricate. It also has to contend with contamination from water vapour and blow-by gases generated by combustion engines.

Depending on how you drive, this can be a problem. Properly warmed engine oil reduces the rate of contamination, but it takes 20 kilometres to actually reach the desired temperatures. That’s right – 20 kilometres. So, for most people, the commute to work or school or the supermarket is saturating the oil with contaminants and not giving the oil enough time to heat and then vaporise the nasties.

When you start your car, oil needs to be able to move quickly to all the moving parts and protectively coat them – which is nigh on impossible when it’s thick with contaminants. In fact, the damage you can cause your engine due to poor quality oil usually occurs on start-up.

And even once it manages to coat all the moving parts, the oil is so contaminated that it’s a much less effective lubricant. Your engine will wear faster.

So how often should the oil be replaced?

Think about what you use your car for. If more than half your journeys are less than 20 kilometres, then you should have the oil changed around 5,000 kilometres, or every six months.

Other factors that affect oil are dusty roads, sustained high speeds and a constantly laden car.

And don’t think you can get around this by simply topping up the old oil with some fresh oil. This doesn’t remove the contaminants, which are the cause of serious damage.

Today’s engines last for around 200,000 kilometres. A well-maintained engine, however, can last for as long as 500,000 kilometres. That’s right – more than double. A regular oil change is a major influence on the life of your engine. So don’t wait for the regular 10,000 kilometre tune-up; protect your car, give it the treatment it deserves, and it will return the favour for years to come.