Next to visiting the dentist, a trip to the mechanic might be the most dreaded appointment for the average Canadian. Innocent maintenance visits have a way of racking up big bills, particularly when your car is no longer covered by warranty. However, like annual dentist visits, regular oil changes are perhaps the single most important step you can take to ensure trouble-free driving. Oil is the life blood of your car’s engine, and it definitely has a life span. Trying to stretch that life can prove fatal.

The Function of Motor Oil

Car engines use oil for two important reasons – lubrication and heat reduction. Though precisely machined, car engine parts are metal and in close quarters with other moving metal parts. A thin coating of motor oil is all there is to reduce friction between these parts and draw away heat resulting from both motion and combustion in the car’s cylinders. Motor oil also has a third job, and that’s to wash away carbon and other by-products of the combustion cycle.

The Oil Filter

Changing the oil filter is an essential part of an oil change, since the filter traps those by-products, dirt and bits of metal so they can’t circulate freely and damage other engine parts. The filter itself is a metal can filled with filter material, usually a synthetic fiber, through which oil is forced before proceeding through the engine to do its dirty work. Cycling back to the oil pump, the fluid is pushed through the filter again for another cleaning cycle. A gasket at the open end of the filter permits a tight seal against leaked from this pressurized system. Like motor oil, filters also have a life span.

Oil Change Intervals


Common rules of thumb are every three months or 5,000 km, though most experts agree that the distance driven is more important than watching the calendar. The by-products you’re protecting against are created by driving, not by time, so changes could be more frequent if you’re driving heavily or less so for second vehicle or through periods of little use.

However, some manufacturers of both cars, oils and filters recommend longer intervals. Check your owner’s manual and follow all recommendations when using longer periods. Oils and filters are not created equally. Don’t expect budget oils and filters to do the same job as the high-performance versions.

The Consequences of Ignoring Oil Changes

When oil breaks down and filters become clogged, the carbon sludge that should be trapped in the filter has free reign to pile up anywhere in your engine. This could lead to special engine cleaning or, worse, replacement of piston rings. Letting the problem go even longer and pistons could seize, damaging other parts and even completely destroying your engine.

As oil breaks down, it loses viscosity. Viscosity describes how thick a fluid is. For example, honey is viscous, but water is not. Oil starts out thick, and this helps it coat and protect engine parts. As it loses viscosity, it becomes thinner, more like water, so it slides off the parts it is meant to coat. It’s also harder for it to hold on to the debris it’s meant to take through the filter.

Old oil equals bad news. Bite the bullet and schedule regular oil changes as mechanical insurance for your car.