The last line of defense between the outside elements and the inside of your car's engine is the air filter. This filter removes contaminants such as soot, carbon, and other abrasives from the air before they can mix with the fuel in the combustion chamber. Even microscopic dust particles can cause damage to important parts of your engine such as cylinder walls, pistons, and piston rings. Since as much as ten-thousand gallons of air must pass through the air filter for every gallon of gas your car uses, a quality filter can prolong the life of your engine. Unfortunately, this important piece of equipment is often overlooked until it's coated with soot and grime. The air filter should be replaced at least once a year, more often if you live in a dusty area. Contact a mechanic or auto parts store in your area for more information on air filters.