That means many households' battered budgets are less able to absorb higher gas prices, especially when the costs of such necessities as food and clothing are rising fast too.
Here are suggestions for saving money on gasoline, with help from the U.S. Department of Energy, Consumer Reports, the Alliance to Save Energy and Edmunds.com.
Don't spill the coffee
The biggest savings will come from avoiding aggressive driving. It can lower your gas mileage by 33 percent at highway speeds and by 5 percent around town.
Imagine a lidless cup of coffee in your car's cupholder. Drive like you don't want to spill it. That means gradual acceleration and gentle braking.
At $4 per gallon, gas savings could range from 20 cents to $1.32 per gallon, based on Energy Department figures. That's a savings of $240 to $1,584 per year for a two-car household with each driving 15,000 miles a year.
Consumer Reports found that slowing from 75 to 55 mph boosted gas mileage 33 percent in testing performed on a family sedan and a large SUV.
Idling yields zero mpg. Don't bother warming up your car or keeping it running while waiting for passengers. The rule of thumb is to turn off your car if you know you'll be stopped for more than 30 seconds, Consumer Reports says.
An extra 100 pounds in your vehicle could reduce your gas mileage by up to 2 percent, or about 8 cents per gallon. Roof junk -- carrying large items on the roof of the vehicle -- creates drag that can cut gas mileage 5 percent.
Cruise control is steadier on the accelerator pedal than you are.
You might try it on lower-speed suburban roads. Edmunds.com called it a "surprisingly effective way to save gas."
Find cheaper gas
Share and compare gasoline prices online at GasBuddy.com, GasPriceWatch.com and gasprices.mapquest.com.
Computerized travel directions from GPS devices or smartphones can help find efficient routes, even among multiple destinations. If you don't have a device, use a website such as www.mapquest.com/routeplanner.
Be on the lookout for promotions and sales that allow you to acquire gasoline station gift cards for free or at a discount. For example, you might be able to redeem credit card rewards points for a gas card.
Make radical changes
Change your work hours to avoid rush-hour traffic. Use carpools and ride-sharing programs. Take public transportation. Walk or bike to work. Or avoid the transportation hassle altogether: work from home.
Here's how to calculate gas mileage:
•Fill your gas tank and reset the trip odometer.
Next time you need gas, fill the tank again. Note the number of gallons you bought.
Divide the number of miles showing on the odometer by the number of gallons showing on the pump. The result is miles per gallon. Most mobile phones have a calculator function that can help with the math.