Don’t let them trip you up: Get an engine flush only if you’ve been driving the car for several years and notice a buildup of greasy material under the oil cap. If a mechanic says you need a flush because your oil is “dirty,” he’s lying.
Fuel injectors should be cleaned, but usually not until they’ve logged a lot of miles (think 100,000 or more). If the mechanic says the ones on your 20,000-mile car are filthy, he’s full of it. However, if you do suspect that there might be a problem with your fuel injectors, play it safe and add fuel-injector cleaner to your gas tank during your next fill-up. Otherwise, if you buy good-quality gas and have a fairly new car, your injectors probably don’t require cleaning.