You've probably heard that motorcycles are more fuel-efficient than cars, and therefore better for the environment. I mean, they're practically bikes, right? It sounds plausible, but how do you find out if it's really true? The same way you find out if ANYTHING is really true: Ask the MythBusters, obviously.

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The Discovery Channel hosts and general experts on everything took on the myth of the green motorcycle on last night's show. (The above image isn't actually from that episode, I just thought it was badass.) Their conclusion: Hogs emit less CO2, and they are more fuel-efficient, so they should probably still be your Mad Max postapocalypse ride of choice. But that doesn't mean the bikes aren't pumping out some nasty crap: hydrocarbons, carbon monoxide, oxides of nitrogen. They emit a lot more of this smog-producing stuff than cars, and we mean a LOT more:

For the most recent model year vehicles tested — from the '00s — the motorcycle used 28% less fuel than the comparable decade car and emitted 30% fewer carbon dioxide emissions, but it emitted 416% more hydrocarbons, 3,220% more oxides of nitrogen and 8,065% more carbon monoxide.

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On average, it's six of one, half a dozen of the other. "At best, it's a wash. Motorcycles are just as bad for the environment as cars. At worst, they're far worse," said host Adam Savage, whom I trust implicitly because it turns out our dogs have the same name.

To be fair, this comparison only covers how green the vehicles are to run. The manufacturing process is a different story, and motorcycles do require fewer raw materials than cars. And they're getting greener, too — improving car efficiency has been on people's radar for a while, but motorcycles are only starting to catch up. It's possible that one day Hell's Angels will be able to walk among hippies with their heads held high.