Observe the Speed Limit

While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph.

As a rule of thumb, you can assume that each 5 mph you drive over 60 mph is like paying an additional $0.20 per gallon for gas.

Observing the speed limit is also safer.

Fuel Economy Benefit: 7-23%
Equivalent Gasoline Savings: $0.20-$0.67/gallon

Drive Sensibly

Aggressive driving (speeding, rapid acceleration and braking) wastes gas. It can lower your gas mileage by 33 percent at highway speeds and by 5 percent around town. Sensible driving is also safer for you and others, so you may save more than gas money.

Fuel Economy Benefit: 5-33%
Equivalent Gasoline Savings: $0.15-$0.96/gallon

Keep Your Engine Properly Tuned

Fixing a car that is noticeably out of tune or has failed an emissions test can improve its gas mileage by an average of 4 percent, though results vary based on the kind of repair and how well it is done.

Fixing a serious maintenance problem, such as a faulty oxygen sensor, can improve your mileage by as much as 40 percent.

Fuel Economy Benefit: 4%
Equivalent Gasoline Savings: $0.12/gallon

Check & Replace Air Filters Regularly

Replacing a clogged air filter can improve your car's gas mileage by as much as 10 percent. Your car's air filter keeps impurities from damaging the inside of your engine. Not only will replacing a dirty air filter save gas, it will protect your engine.

Fuel Economy Benefit: up to 10%
Equivalent Gasoline Savings: up to $0.29/gallon

Keep Tires Properly Inflated

You can improve your gas mileage by around 3.3 percent by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer.

Fuel Economy Benefit: up to 3%
Equivalent Gasoline Savings: up to $0.09/gallon

Use the Recommended Grade of Motor Oil

You can improve your gas mileage by 1-2 percent by using the manufacturer's recommended grade of motor oil. For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1-2 percent. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1-1.5 percent. Also, look for motor oil that says "Energy Conserving" on the API performance symbol to be sure it contains friction-reducing additives.

Fuel Economy Benefit: 1-2%
Equivalent Gasoline Savings: $0.03-$0.06/gallon

Remove Excess Weight

Avoid keeping unnecessary items in your vehicle, especially heavy ones. An extra 100 pounds in your vehicle could reduce your MPG by up to 2%. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones.

Fuel Economy Benefit: 1-2%/100 lbs
Equivalent Gasoline Savings: $0.03-$0.06/gallon

Source: United States Department of Energy