5 clean diesels: The future is now

The first of many diesel-powered Audis will be the 2009 Q7 TDI. Expect diesel-powered A3s and A4s to follow in short order. The Q7 is a seven-passenger crossover, which is defined as either a station wagon or a minivan depending on your age. Its turbocharged 3.0-liter diesel engine makes peaks of 221 horsepower and 406 pound-feet of torque. The Q7 will make about 25 miles per gallon on the highway: That's five better than the gasoline-fueled six-cylinder Q7 and seven better than the V8 Q7. With the optional towing package, the Q7 diesel can pull a trailer weighing a heavy 6600 pounds.

Audi is among the most experienced diesel makers. It has sold more than 4.5 million diesel vehicles and won the 24 Hours of Le Mans with a diesel-powered race car.