Idaho Transportation

Office of Communications
P.O. Box 7129
Boise, ID 83707
Fax: 208.334.8563


How you drive can influence your pain at the pump

This information was provided by Cheryl Rost, manager of ITD Safety and Risk Management. The tips can squeeze a little extra gas mileage out of your vehicle and leave you with a few extra pennies when you fill the gas tank.

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.

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.

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 percent. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones.

Avoid excessive idling
Idling gets 0 miles per gallon. Cars with larger engines typically waste more gas at idle than do cars with smaller engines.

Use cruise control
Using cruise control on the highway helps you maintain a constant speed and, in most cases, will save gas.

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.

Check and 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.

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.

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.

Don't top off
Topping off the gas tank can result in your paying for gasoline that is fed back into the station's tanks because your gas tank is full. The gas nozzle automatically clicks off when your gas tank is full. Gas station pumps are equipped with vapor recovery systems that feed back gas vapors into their tanks to prevent vapors from escaping into the air and contributing to air pollution. Any additional gas you try to pump into your tank may be drawn into the vapor line and fed back into the station’s storage tanks.

Tighten up that gas cap
Gas will evaporate from your car's gas tank if it has an escape. Loose, missing or damaged gas caps cause 147 million gallons of gas to evaporate each year, according to the Car Care Council. So be sure to tighten up that gas cap each time you fuel up your car.

Go for the shade
The hot summer sun that makes the inside of your car feel like a sauna also zaps fuel from your gas tank. "If you let your car bake in the sun there's going to be a greater amount of evaporative emissions that take place than if you park in the shade," says Jim Kliesch, research associate at the American Council for an Energy-Efficient Economy and vehicle analyst for So park your car in the shade of a building or tree whenever possible. And buy a good windshield shade. A windshield shade blocks sunlight and helps to keep heat out of the inside of your car.

Use your garage for your car
Got a garage? Clear it out and make room for your car. Parking in your garage will help your car stay warm in winter and cool in summer, and you won't have to depend as much on your gas-guzzling air-conditioning or defroster when you drive.

Planning and combining trips
Combining errands into one trip saves you time and money. Several short trips taken from a cold start can use twice as much fuel as a longer multipurpose trip covering the same distance when the engine is warm. Trip planning ensures that traveling is done when the engine is warmed-up and efficient.  With a little planning, you can avoid retracing your route and reduce the distance you travel as well. You'll not only save fuel, but also reduce wear and tear on your car.

If you can stagger your work hours to avoid peak rush hours, you'll spend less time sitting in traffic and consume less fuel. If you own more than one vehicle, drive the one that gets the best gas mileage whenever possible.  Consider telecommuting (working from home) if your employer permits it.

If possible, take advantage of carpools and ride-share programs. You can cut your weekly fuel costs in half and save wear on your car if you take turns driving with other commuters. Consider using public transit if it is available and convenient for you.

A roof rack or carrier provides additional cargo space and may allow you to meet your needs with a smaller car. However, a loaded roof rack can decrease your fuel economy by 5 percent. Reduce aerodynamic drag and improve your fuel economy by placing items inside the trunk whenever possible. Avoid carrying unneeded items, especially heavy ones.


Published 7-4-8