Proponents of diesel-powered cars drove to Capitol Hill Thursday hoping to distance themselves from a questionable image that the engines and vehicles have had with consumers in the past.
None of the vehicles had the telltale dirty rear panel -- soiled with an oily, sooty film from diesel exhaust -- yet all had the characteristic rattling sound of a diesel engine.

"If you put a diesel beside a gasoline, it's really not that much difference," Schaeffer said. "The consumer is only going to notice the difference where it counts -- and that's at the pump. They're going to be spending less on fuel, about 30 percent less, with a diesel as compared to a gasoline model."

The group hopes to persuade congressional lawmakers to support White House plans for tax incentives to encourage people to buy diesel-powered vehicles.