Burger and fries to go Hey, you, environmentalist: Want the greenest wheels going but find yourself lacking $109,000 for a Tesla Roadster? Despair not! There's a vehicular option that makes a Prius seem like a gas guzzler and can save you major bucks, too. (Here's the only catch: This option may not be strictly legal under the federal Clean Air Act. But more on that later.) The vehicle in question is a grease car, a ride capable of lowering your motoring greenhouse gas emissions by 78 to 87 percent over regular gasoline. A grease car is a diesel car, truck or Jeep that runs on waste vegetable oil from your local greasy spoon or fine-dining establishment. A grease car also significantly reduces a bevy of environmental badness -- asthma-triggering particulate matter, smog-forming carbon monoxide, likely carcinogenic polycyclic aromatic hydrocarbons and the sulfur emissions that lead to acid rain. The only environmental downside is a small increase in smog-forming nitrogen oxide....