Contaminants tend to accumulate in all engines as the miles add up. Short-trip, stop-and-go city driving, as well as excessive idling, accelerate the rate at which these contaminants form. Changing the oil and filter regularly and using gasoline that contains an adequate amount of detergent to keep the fuel system, valves, combustion chambers and pistons clean, are all ways to keep these contaminants in check.

But many motorists don't maintain their vehicles as well as they should. Oil changes are put off far too long. If harmful contaminants are not removed from the engine, they eventually will cause major problems.

Changing Time
All engines experience a certain amount of blowby when they run. Unburned fuel, water and other combustion byproducts blow past the rings and end up in the crankcase. The higher the mileage on the engine, the greater the amount of blowby. The PCV system siphons most of these vapors and moisture back into the intake manifold, which helps keep the oil clean and reduces the formation of acids, varnish and sludge. But if the PCV system isn't working, is plugged up or the oil isn't changed often enough, the oil soon becomes saturated with contaminants, and sludge starts to form inside the engine. If this sludge is not removed, it can be very damaging and will eventually cause the engine to fail.

Motor oil contains detergent additives that neutralize blowby contamina...