Even the cleanest gasoline may contain small amounts of water and dirt. Your car's fuel filter helps protect fuel system components by removing these contaminants before they get to the engine. Dirty fuel can be a major cause of poor engine performance and low fuel economy. It can also clog up the carburetor or injectors and possibly cause major damage to your car's engine. Fuel filters vary widely in type and location according to what kind of car you have. Some cars have two filters. One is for removing dirt particles, and the other removes water. It may be a good idea to have your fuel filter replaced on a yearly basis, more often if the fuel supply you use isn't clean. When your fuel filter becomes slightly clogged, your car may run fine when idling but start sputtering or losing power at higher speeds. If your fuel filter becomes blocked completely, the engine may stop. Contact an auto parts store or a local auto mechanic for more information on your car's fuel filter.