“Check out the Volkswagen TDI. “
Cleaner than most gasoline engines. VW and Audi use TDI, in several models.
And Audi has won 24 Hours of LeMans 11 of the last 13 years, recently with diesel TDI. This year with a TDI Hybrid.
Cheapest model is a Jetta sedan, and I think the Golf is about the same price—low $20s, up to about $28,000 for a Jetta wagon, automatic, sunroof, navi etc.
30 mpg city, 40 mpg highway and reports are they do better than these ratings.
(That's why I have one!)
You get really used to that 600 miles on a tank..;-)