Just because a car has low fuel efficiency doesn't mean it's the worst polluter on the road. The Chevrolet Suburban and Dodge Challenger are some of the biggest gas-gulpers available, but they don't cause quite the environmental harm other cars do.
That title is reserved for vehicles that combine their poor gas mileage with high tailpipe and greenhouse gas emissions. Think along the lines of some of the bulkiest cars on the road, like the Jeep Grand Cherokee, Chevrolet Trailblazer and Dodge Dakota.
While fuel economy is linked to emissions, it's not the only factor. Pollution levels also have to do with the type of fuel being used and the age and condition of the engine, among other things.
You can have a really fuel-efficient, dirty vehicle and a really clean, not-so-fuel-efficient vehicle," says Karl Simon, a director of compliance and innovation for the EPA's Office of Transportation and Air Quality. "It really is pretty wide open from a technical perspective."