Apr. 19--BOULDER, Colo. -- For $700, a truck repair shop northeast of Erie will turn your car, your truck -- even a big rig -- into a "hybrid."

And that's before you apply the alternative fuel vehicle credit from the federal government, which allows you to write off 30 percent of the cost on your taxes.

Sound too good to be true?

As the 40th Earth Day approaches this week, people across the country are being deluged with claims of greenness and tantalized with the latest ways to become greener themselves. But, in the sophisticated, science-laden world of global warming, where supercomputers spend weeks crunching the numbers for just one climate model, it can be tough to separate the truly green pioneers from the snake oil eco-salesmen.

But one maxim holds true: If it seems too good to be true, it probably is.

"It's one thing to say you're green, but it's another to make the tough choices," said Carl Lehrburger, whose Fort Lupton company works on ways to use biomass as a replacement for oil. "Consumers have run awry without asking the big questions about consuming."

The flood of green advertising washing over America has managed to tout something environmentally friendly about nearly every imaginable product, giving people the opportunity to be "green" without changing their lifestyles. Even the Hummer, a vehicle that has, for some, come to symbolize the excessive American lifestyle, is in on the green game.

"Thirst for adventure. Not gas." reads one recent Hummer billboard.

"Green marketing really became en vogue, and the critical thinking that goes into dissecting these policies -- it has really been lacking," Lehrburger said. "You can see it in the energy debate. The efficient Hummer? From a rational point of view, it's just loaded with self-interest."

Dreaming of fuel efficiency

Twin Peaks Diesel in Frederick has recently begun installing the "Hydro Cell Generator" in cars and trucks -- and customers are raving about it, claiming that the gadget can increase fuel efficiency from 25 percent to 35 percent.

"All it takes is a cup of water," said Aaron Frank, who runs the shop.

The hydro cell uses electricity from the car's battery to split water into hydrogen and oxygen, a process called electrolysis. The hydrogen is then pumped into the fuel intake, adding extra power and, proponents claim, extra miles to the gallon.

And while the claim isn't all false -- the battery can split the water, and the hydrogen does get pumped into the engine and burned -- the big-picture view isn't as rosy.