1 minute (AAA)

Driving at 55 mph instead of 65 mph can improve your gas mileage by how much?

15 percent (EPA)

Will using high-octane gas improve my mileage?

Unless your car was designed explicitly for it or your engine is knocking, high-octane gas is a waste of money. (Source: Federal Trade Commission)

I've seen advertising for various "gas-saving" automotive devices and oil or gas additives. Will these products really help my gas mileage?

The FTC has advised consumers to be wary of these gas-saving claims. Even for the few that have been found to work, the savings have been small.

Which uses more gas when driving on the highway, having the windows open or using the air conditioning?

Running your A/C does consume slightly more fuel. So if you are driving slowly, you may be better off leaving your windows open, according to Edmunds.com. But at 65 mph, any extra fuel used by A/C is made up for by better aerodynamics. There's not enough difference to worry about using either, though, says Consumer Reports.

Does it make any difference in fuel consumption if I run several errands in one trip?

Yes. Your car uses more gas when the engine is cold than when it's warm. According to the Department of Energy, several short trips taken from a cold start can use twice as much fuel as a single trip that covers the same distance.

Because a car uses more gas when the engine is cold, shouldn't I warm up my engine before I leave for work in the mornings?

The best way to warm up the engine is to drive the car. Modern engines need little warm-up; they're most efficient when being driven. (Source: U.S. EPA)

The EPA mileage posted on a new car is based on a properly maintained vehicle. Driving a car in sub-par condition can reduce your mileage by how much?

Between 10 percent and 20 percent. According to the FTC, a poorly tuned engine can reduce gas mileage by 4 percent. Underinflated tires can reduce mileage by up to 3 percent.

And a dirty or clogged air filter can reduce your mileage by a whopping 10 percent.

What is the biggest gas waster?

According to www.fueleconomy.gov, aggressive driving can lower gas mileage by 33 percent at highway speeds and by 5 percent around town.

(Compiled by Staff Researcher Peggy Neal)