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.

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.

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.