Don't Buy That New Prius! Test-Drive a Used Car Instead

In 2006, an Oregon market research firm released an incendiary 500-page report. Its claim: A Humvee (13 miles per gallon city, 16 highway) uses less energy than a Prius (48 city, 45 highway). Scientists quickly debunked the study, but the Hummer lovers got one thing right. Pound for pound, making a Prius contributes more carbon to the atmosphere than making a Hummer, largely due to the environmental cost of the 30 pounds of nickel in the hybrid's battery. Of course, the hybrid quickly erases that carbon deficit on the road, thanks to its vastly superior fuel economy.

Still, the comparison suggests a more sensible question. If a new Prius were placed head-to-head with a used car, would the Prius win? Don't bet on it. Making a Prius consumes 113 million BTUs, according to sustainability engineer Pablo Päster. A single gallon of gas contains about 113,000 Btus, so Toyota's green wonder guzzles the equivalent of 1,000 gallons before it clocks its first mile. A used car, on the other hand, starts with a significant advantage: The first owner has already paid off its carbon debt. Buy a decade-old Toyota Tercel, which gets a respectable 35 mpg, and the Prius will have to drive 100,000 miles to catch up.

Better yet, buy a three-cylinder, 49-horsepower 1994 Geo Metro XFi, one of the most fuel-efficient cars ever built. It gets the same average mileage as a 2008 Prius, so a new hybrid would never close the carbon gap. Sure, the XFi has no AC or airbags — but nobody said saving the planet would be comfortable, or even safe.