DriverSide's Car Dictionary has the most comprehensive definitions of automotive terms. This auto glossary can help you decipher what your mechanic is fixing and what the purpose or function of the particular auto part or accessory is for. We have taken the mystery out of automotive service jargon, so that you don't have to.
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.