"Auto mechanics repair and maintain cars. Some mechanics work on all parts of any car, while others specialize in one area or on one type of car. The most challenging aspect of car repair is often the mechanic's favorite part: diagnosing the problem. Speed and accuracy in diagnosis and quoting prices to the customer are crucial if the mechanic intends to keep long-term clients. The mechanic examines the engine while it is running (if possible) to see if his initial assumptions are correct. Electronic diagnostic equipment is useful but the good mechanic can tell a lot by using eyes, ears--even nose--as he searches for problems and potential hazards. Sometimes he repairs parts, but if the part is worn or damaged, he replaces it. Some mechanics compare their field to that of the physician, because most people come in only when their car is in dire straits, not when regular preventive maintenance could have avoided the problems altogether.