Another Drive Greener Tip: Regularly check and replace dirty air filters
An auto air filter that is clogged with dirt, dust and bugs chokes off the air and creates a “rich” mixture* that causes the engine to lose power. Replacing a clogged air filter will improve your car’s performance and acceleration. The air filter should be inspected at each oil change, and replaced annually or when restricted, torn, water or oil-soaked.
*"rich fuel mixture defined"
There is an ideal mix of air and fuel. Too much air causes a "lean" condition, while too much fuel produces a "rich" condition. Most vehicle's are "rich" from the factory because it is generally safer than a lean condition (lean conditions yield high exhaust gas temperatures that can damage other parts, and are unsafe). A "little" rich is common; overly-rich is not good, and some symptoms of a rich mixture include excessive soot on the exhaust tip, and a noticeable drop in fuel efficiency.