While electric and hybrid cars are rightfully drawing a lot of attention in the auto world, there's another technology that investors are probably overlooking: clean diesel. With the sulfur content now reduced by 97%, today's diesel offers near-zero emissions and is about 30% more fuel-efficient than gasoline.

The big three of Ford (NYSE:F), General Motors (NYSE:GM), and Chrysler are dominating the light truck and auto diesel market in the U.S., with sales growing nearly twice as fast as the general market. What's more, Chevrolet and Volkswagen's (NASDAQOTH:VLKAY) Audi division are offering up some groundbreaking new autos this year.

Fool analyst Rex Moore spoke with Allen Schaeffer of the Diesel Technology Forum at this year's Washington Auto Show. In this installment of the multipart interview, Schaeffer talks about the growing number of choices in the diesel segment.

Rex Moore has no position in any stocks mentioned. The Motley Fool recommends Ford and General Motors and owns shares of Ford. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.