JKB, I drove a vehicle that got in the low 20's (mpg) to work, and did some numbers crunching. I was driving 75 miles a day round trip, and buying a VW Jetta Diesel was a logical choice. Even with higher diesel prices, the savings in $$ spent on fuel was enough per month to equal a car payment.
I bought one and was glad that I did. The only drawback is in the deep snow - it doesn't have the ground clearance that a truck does. But, with snow tires on it I've never gotten stuck.