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Why Change My Car's Oil?

Get the lowdown on oil and your car's engine.

Neglecting your engine is a lot like forgetting to brush and floss your teeth: The damage isn’t immediate, but it compounds over time. Of course, automotive oil lubricates your engine’s moving parts. But beyond minimizing friction and heat, oil contains chemical additives such as antioxidants, detergent, and emulsifying agents that improve viscosity and fight corrosion and rust.

Over time, contaminants and moisture inevitably accumulate within the engine and the oil. If you skip your regular recommended change, the oil in your car gets thicker and begins to jell. A hard-to-remove black sludge develops and binds to everything it touches. When the engine heats up, the sludge crystallizes, continuing the vicious cycle: less lubrication, more friction, more contaminants. As it builds up, the sludge leads to a host of problems, from decreased power output and gas mileage to the failure of gaskets, belts, and eventually the entire engine.

Your best bet is to follow the manufacturer’s recommended oil change schedule, and swap the filter while you’re at it to avoid sullying the fresh oil. Using the proper grade of oil at the appropriate interval can improve your gas mileage too, saving you up to 6 cents per gallon. That may not sound like much, but it does add up. On top of that, you just might be spared the cost of a new engine.

AAA can help with purchasing, insuring, and maintaining a vehicle. To learn more, contact any branch office or visit


This article was first published in July 2010. Some facts may have aged gracelessly.