Many gas pumps have additives available at your fingertips -- just push a button and they're instantly mixed with the gas as you fill up.

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Fuel and Oil Additives

The variety of additives, octane boosters and fuel system cleaners is staggering; it's easy to find the long racks of these products in any auto parts store. Some claim to clean carbon deposits out of your engine, while others claim to enhance fuel or oil performance through a variety of chemical reactions. Still others claim they coat engine parts, reducing friction and extending engine life.

It's hard to lump all of these additives into the hoax category, since some do indeed clean internal engine parts, and others may contain lubricants that don't harm the engine. But be wary of putting an additive into your car without first checking its contents: Some additives can damage modern cars' engine sensors, leading to expensive repairs. Additives are all different, so you're wise to research anything you plan to put in your gas tank or oil pan [source: Tony's Guide to Fuel Saving Gadgets].

In a world of mileage-hoax gadgets, are there tips, techniques or devices that will actually improve your mileage? There are, according to the U.S. Environmental Protection Agency and the U.S. Department of Energy. It may be surprising, too, that these mileage boosters often require little or no investment.

Proper car maintenance is a major key to getting the best mileage that your car is capable of achieving. A smooth-running engine and well-lubricated drivetrain not only keep your car running longer, but they also contribute to a more enjoyable driving experience. Consult your owner's manual to learn your cars recommended service intervals.

Driving techniques also play a big role in maximizing your mileage. Smooth stops and starts help you avoid wasted energy: A car burns more gas getting up to speed in a hurry than it does during gradual acceleration. Likewise, using the brakes in a sudden, jerky manner can waste energy, requiring more gas to get the car back up to cruising speed.

Finally, considering what's in your car can make a difference in how far your car goes on a gallon. A trunk or pickup bed full of heavy, unnecessary items hurts mileage. A simple thorough cleaning can do as much for your mileage in some cases as the latest fuel-saving gadget could ever hope to do [sources: U.S. Environmental Protection Agency, U.S. Department of Energy].

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