They have been around almost as long as cars; those devises claiming to increase fuel mileage. It seems whenever gas prices take a hike, they always seem to surface. They range from magnets on fuel lines, to small fans in the intake all the way to additives for the fuel and special air filters.

While they may increase the wallet thickness of those that pedal them, I have seen no evidence that they increase anything else. The fact is it takes a certain amount of energy, to move a certain amount of weight, a given distance at a given speed with a given engine design. Gadgets added to that engine will not change that.

Another myth is that replacing an air filter will increase mileage. On any modern vehicle, with fuel injection, which is almost every vehicle on the road, a dirty filter may reduce power, but not mileage. With the old carburetors, that cars used years ago, there was a grain of truth. A dirty air filter would raise intake manifold vacuum, and draw more fuel from the carburetor jets. On present day vehicles, fuel is monitored by the air flow meter, the oxygen sensors and other sensors.

Replacing a dirty air filter is always a good idea, but replacing a filter for the purpose of a mileage increase will be disappointing. For ideas that will work, see our article entitled Free Gasoline.