[Diesel_Dave]

A vehicle that gets better mileage (and doesn't give up other factors like performance, etc.) costs more to produce--otherwise they would already do it. If the customer is willing to pay the extra $ for the extra FE, then they make the car. It's really as simple as that.

Look at the Prius--it gets good FE, but it cost a bunch too.

Imagine if we got everybody on this site together and gave them unlimited resources to create the ultimate mpg machine (isn't that a COOL thought!). I think we could probably make a sedan that would get over 100 mpg (on gas or diesel). However, with all the added technology we'd have to charge $50k for the thing to make a profit. Most people simply wouldn't pay for it.