Here’s an interesting suggestion for saving gasoline, your bank account and the environment: Forget about how many miles per gallon your car gets.

A couple of professors at Duke University have been promoting the idea this month after determining that the math-challenged American public is fairly confused about fuel efficiency because of our fixation with mpg.

And it’s not as crazy as it sounds.

Consider this example: Smith trades in a 10 mpg SUV for a slightly less inefficient 15 mpg SUV. Jones, meanwhile, almost triples his fuel efficiency by trading in a 20 mpg minivan for a 55 mpg hybrid.

Who is going to cut their gas usage more? Smith, the SUV driver.

In fact, assuming they both drive 15,000 miles a year, Smith will save $2,000 worth of gas and Jones will save $1,908. Now I, too, had understood there would be no math in this column. But times are pretty desperate with gas now rising toward $4.10 a gallon, and here is a case where a little math could change the way you look at the vehicles in your driveway and how you approach your next purchase.

The business professors at Duke started talking about fuel economy and mpg while carpooling to work in a hybrid. Then they asked college students trick questions like the one above, only not so obvious.

For example, which would save more gas: a) upgrading from 16 to 20 mpg, or b) upgrading from 34 to 50? The correct answer is a, although the college students tended to say b.

That led to an article in the journal Science, a call for a national math lesson and a lot of head scratching. “It’s been nice to get the word out,” said Jack Soll, one of the professors.

What’s basically happening here, mathematically speaking, is a case of diminishing returns.

Even a small gain in mpg for a gas-guzzler can have a huge impact on fuel consumption simply because it’s burning so much more to start with. Getting 5 mpg more out of a Ford F-150 could save $1,500 a year.

More fuel efficient vehicles, on the other hand, are already using less, so cutting their consumption by the same percentage carries a much smaller savings. Getting 5 mpg more out of a Honda Civic could save $200 a year.

Of course, trading in the F-150 for the Civic is the best deal all around, excluding cargo space, of course. The professors took pains to say that improving fuel efficiency is a good thing no matter what you’re driving.

But, if you’re looking to compare fuel efficiencies and the cost of driving one car against another, they said, forget mpg.

A much better way, they said, is to figure out “gpm” – or how many gallons it takes to drive your car 10,000 miles. Using gpm, you see that improving from 10 to 15 mpg will save 333 gallons of gas every 10,000 miles, while going from 30 to 50 will save 133 gallons.

For a more complete explanation and chart, see this Science Daily article (http://www.sciencedaily.com/releases/2008/06/080619142118.htm).

The Duke research isn’t likely to change American car ratings from mpg to gpm any time soon. But, given the cost of a tank of gas, a little math won’t hurt us.

If California, Maine and 10 other states ever do implement new fuel efficiency standards to combat global warming, it seems they’ll have to overcome heavy duty opposition from more than just the auto industry.

U.S. Rep. Henry Waxman, D-Calif., wrote a letter to President Bush Monday asking him to repudiate a behind-the-scenes lobbying effort against the states by Bush's Transportation Secretary and others. Waxman presented a trail of internal administration e-mails that suggest the effort was approved by the White House and was aided by the auto industry.

Federal courts have so far supported California’s plan to make cars and trucks more fuel efficient, despite the automakers’ argument that there should only be one nationwide set of standards. But California also needs a waiver from the U.S. Environmental Protection Agency, and Gov. Arnold Schwarzenegger has been threatening a lawsuit if the agency doesn’t make a decision soon. When, or if, California gets permission, Maine and the other states can follow by requiring the California standards.

Waxman said his committee, the House Committee on Oversight and Government Reform, found evidence that the administration was improperly trying to give the EPA grounds for a denial of the waiver by lobbying federal legislators and governors to come out in opposition to California’s plan.

A spokeswoman for White House Council on Environmental Quality said the communications were appropriate and routine.

Here is an Associated Press story on the accusations.

And here is Waxman's letter and the e-mails.

The results are in, finally, from our “What’s-In-Your-Driveway” poll of the Maine congressional delegation.

As promised in an item posted last week, Down to Earth asked each of our four members of Congress what vehicles they use and whether they lease any cars at taxpayer expense. The questions grew out of a debate in the House of Representatives over whether to require members with taxpayer-financed vehicles to give up gas guzzlers for “low greenhouse-gas emitting vehicles.” As of last year, 136 of 435 House members were leasing cars at taxpayer expense.

It took anywhere from 10 minutes to five days for the press secretaries of all four members to give us the answers. Now, there are a lot more important things going on in Washington than our pesky poll, so we won’t name the slowpokes. Here are the responses in the order they were received.

The fuel-efficiency debate is getting a little personal in Congress.

A congressman from Missouri who travels in a van fueled by cooking grease wants to require that his colleagues who lease vehicles at taxpayer expense downsize into “low greenhouse-gas emitting vehicles.” He actually got the language into a major House energy bill, although it’s facing resistance from colleagues, including ones who get around their districts in SUVs or luxury cars.

The Kansas City Star found last year that 136 of the 435 House members, including members of both parties, were leasing cars at taxpayer expense. Here is a story the newspaper published this week about the fuel efficiency debate.

Now, it’s generally a good idea to focus on one’s own carbon footprint before pointing the green finger at someone else. But, these are vehicles we taxpayers are paying for and these are elected officials who are debating legislation to get us out of our gas guzzlers.

Seems like a good time to poll our Congressional delegation, yes? We’ll find out whether or not any member has a taxpayer-financed vehicle, and, if any do, what kind of vehicle it is. And, while we’re at it, we’ll find out what other vehicles they use. I'll post the answers as soon as I get 'em.

A contingent from Maine – led by Department of Environmental Protection Commissioner David Littell – is in Arlington, Va., today to be part of a peaceful revolt against the federal government and the U.S. auto industry.

Littell and Adam Lee, president of the Lee Auto Malls, were expected to testify at a hearing being held by the U.S. Environmental Protection Agency. Also with the delegation is Steve Hinchman, an attorney with the Conservation Law Foundation in Brunswick. All three were strong advocates of Maine’s law to increase car and truck fuel efficiency as a way to fight global warming emissions.

The agency is considering a waiver to allow Maine and at least 10 other states to push ahead with their own efficiency and emissions standards even though they are more strict than the federal ones. The leader of the rebellion is California, which has established a legal right to adopt air pollution laws as long as it gets EPA approval. And once California sets a new standard, the other states are allowed to follow.

The auto industry is fighting the latest California initiative in court, but the blessing of the EPA is considered an even bigger potential obstacle. The hearing today comes six weeks after the U.S. Supreme Court rebuked the EPA for not regulating greenhouse gases. But some advocates for the stricter standards are now accusing the Bush administration of setting out to stall any added regulation as long as it’s in office.

Here’s a sample of that criticism in a column written by Arnold Schwarzenegger and Connecticut Gov. M. Jodi Rell, both Republicans, and published in The Washington Post on Monday.

Here’s an Associated Press story about the hearing. We’ll have the updated story and comments from the Maine participants in tomorrow’s paper.

Is your relationship with your car a little strained? Your vehicle gotten a lot more needy lately?

Feeling a little restless, perhaps?

Well, with gasoline back in the neighborhood of $3 a gallon and all the focus on the greenhouse gas coming out of your tailpipe, nobody would blame you. But, what are you gonna do? Walk?