Interested in saving money?

Today, the Alliance to Save Energy, a national advocacy group, is launching a Drive $marter Challenge, with an interactive web site that offers gas-saving tips in Spanish and English, as well as coupons and links to information on local gas prices, public transportation, biking, car sharing, and carpooling.

All this comes not a moment too soon, with gas prices careening toward $4 and the summer driving season upon us.

The website (if it doesn't work, you have to install Adobe Flash player) has a calculator allowing drivers to enter specific vehicle data (make, model, year, cylinders) and find out how much money they can save by changing a few things.

The Wal-Mart Foundation and 16 other partners are joining the campaign.

The web site's calculator also displays a running tally of the cumulative money, gallons, and CO2 emission savings of everyone who has "taken the Challenge" by pledging to follow through on any or all of those fuel-saving steps. The point is that even small efficiencies can add up significantly.

Some of the tips are ones we already know, but still can't seem to do. Like slowing down or, heck, just obeying the speed limit. Want an example? Speed data from the New Jersey Department of Transportation shows that on one stretch of I-295 through Burlington County, in 2006, as many as 75 percent of all drivers exceeded 65 miles per hour.

The campaign adds data to give more oomph to the suggestions. For instance:

An extra 100 pounds in the trunk cuts a typical vehicle's fuel economy by two percent. It would be like adding 8 cents a gallon to $4-a-gallon gas.

Inquirer reporter Tony Gnoffo wrote a story not long ago about other fuel economy measures, including tips from "hypermilers" who have got to be the all-time experts for cranking out the mileage.

More tips -- although not as flashily presented -- are at the "greener cars" website of the American Council for an Energy Efficient Economy.

If you want to really parse out the savings, follow  the lead of UPS, the package delivery company, which  discovered that planning clockwise routes — with right-hand turns — is better than counterclockwise. In 2007, the company shaved nearly 30 million miles off its routes and saved 3 million gallons of gas. Read about it here.

Since I drive a Prius, which has a constant mileage readout, I've seen the savings you can get by driving more slowly and more gently.

I have another tip I realized just yesterday, when I had the radio on and I suddenly realized my speedometer had crept up to 65:  Don't listen to loud rock music while driving!