While electric and hybrid cars are rightfully drawing a lot of attention in the auto world, there's another technology 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:VWAGY) 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 multi-part interview, Schaeffer explains why investors need to look beyond the buzz of electric vehicles.