Greg Melville does a smart thing at the start of "Greasy Rider: Two Dudes, One Fry-Oil Powered Car, and a Cross-Country Search for a Greener Future" -- he allies himself with the common man who is all for doing right by the environment -- when it's convenient.

"I only take a stand on something when I think I'm getting screwed," Melville explains on page 2.

When the time comes for he and his wife, Ann Marie, to get a second car, Melville lobbies for a pickup with a big throaty V-8, red and glistening with chrome, a monster truck with which he dreams of "shifting into four-wheel drive, and crushing a Prius beneath my fat tires."

His wife responds with an icy stare. How about buying a diesel and converting it to run on vegetable oil? "You'll save a lot of money," she argues, appealing to his cheapness.

So he does, buying a $4,300 1985 Mercedes 300TD wagon and a conversion kit. Then, struck by a sense of adventure and that cheapness, he gets the notion to drive cross-country on used vegetable oil begged from restaurants along the way. Idea morphs into action when he discovers that the first person to drive an automobile across the U.S -- H. Nelson Jackson, in 1903 -- was also from his home of Burlington, Va.

With a vague plan in place, he enlists Iggy, an old college roommate, to tag along. Iggy quickly proves less Tonto to Melville's Lone Ranger than Sideshow Bob to Krusty the Clown.

"I'm a totally courteous driver," Melville proclaims after getting cut off by an aggressive Honda driver.

"What are you talking about?" replies Iggy. "I remember you in Washington, D.C. You drove like a complete jerk!"

To make things more interesting, Iggy has a healthy dose of green skepticism. He challenges Melville to find a greener America by assigning a series of side trip "errands" for Melville to run.

The errands provide informative relief to what otherwise might be a long ride with two snippy ex-roommates.

One errand takes them to what Melville is certain must be the ultimate green home, Al Gore's 10,000-square-foot Belle Meade mansion in Nashville. The former vice president and Nobel Prize winner's do-as-I-say cred is quickly eroded when Melville learns that the house has a monthly power bill of $1,200 and burns 191,000 kilowatt hours of electricity in a year, "or enough to power seventeen typical American homes." When they drive by Gore's mansion one night. the house appears empty, but is "lit up like the freaking Taj Mahal."

Other errands include a trip to a Minnesota wind farm (initially intended to supply power for a hog farm but which provides power to 3,000 homes); a visit to the National Renewable Energy Laboratory (where an official tells Melville veggie oil is "bringing about your car's premature death"); a green Wal-Mart (with a broken windmill out front, which the greeter proudly says, "It doesn't work now, but it has worked"); and a visit to Fort Knox, known as a gold repository but home to a geothermal heating system that taps into the layer of earth below the frostline where a constant temperature of 57 degrees is maintained. In the summer, the system cools buildings; in the winter a supplemental heat pump brings the temperature up a few degrees to a comfortable level. Begun as a pilot project in 2001, the system has been expanded to provide heat and cooling to 3.5 million square feet on the compound and has reduced Fort Knox's natural gas bill by $10 million a year.

Which brings up another smart thing Melville does: He uses facts and figures sparingly. Those few numbers about Fort Knox tell you what you need to know about whether the system works.

Sometimes, Melville does the job with even less digital distraction. "Four out of five grease-power drivers agree that the worst part of owning a veggie car is asking for oil at restaurants. All right," he adds, "I made that number up, but it's probably fairly accurate."

Melville cleanly establishes himself as just another guy looking for answers. In his search to separate the wheat from the chaff on environmental issues, he avoids the pitfall of too many green books that make it clear going in that they have the answers before asking the questions.

When the men finally reach their destination -- the BioFuel Oasis fryer grease station in Berkeley, Calif. -- Melville makes clear he doesn't have all the answers. "If two goobers like us can drive across the country without fossil fuels or putting a lot of carbon into the air, the answers for sustainability are easier than people think," he tells Iggy.

Then, cementing his everyman cred, he writes: "I was too sweaty and tired to be more philosophical than that."

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