... record levels, fuel purchases still take a painful bite out of the family budget. Myths and legends tend to pop up anytime a subject is popular. Schemes for increasing gas mileage can be found all over. Let's take a look at some of the myths about saving fuel.

Myth One: Replace your air filter

Many people swear that replacing their air filter regularly results in increasing gas mileage. A clean air filter is supposed to supply your engine with cleaner air filled with more oxygen, increasing your engine's efficiency. Engines running more efficiently need less fuel to provide more power. This might be true if you drive an older vehicle (say 1980s or earlier). However, today's vehicles are filled with sensors and computer chips. As your air filter begins to collect dirt, your engine senses the amount of oxygen available and sets your air-fuel mixture to compensate. So, assuming your sensors are operating correctly, changing your air filter is likely to have no effect. Myth busted.

Myth Two: Over-inflate your tires

A popular proposition for increasing gas mileage is to pump up your tires. By increasing the pressure in your tires, you are decreasing the amount of the tire that's in contact with the road's surface. This shrinks friction and rolling resistance, so you need less horsepower to push the car along the highway. Although the idea makes sense, lab and road testing at edmunds.com found no measurable difference. It's a good idea to inflate to recommended levels, but anything beyond that is ineffective, and maybe even unsafe. Myth busted.