Definitely get the diesel. In the past, I've driven the gasoline-powered Audi Q7, and found it overwhelmingly large and difficult to maneuver in city traffic. But with a great diesel engine, this behemoth is transformed; I realize now it's not as large as I originally thought. The better powerplant gives the Q7 the grunt it needs to shrink around you and feel almost agile. City streets are a breeze, and the freeway is relaxing to drive whether you're coasting with traffic or rushing to the airport. Audi makes some of the best diesel engines available, and this one really has no drawbacks. It is as quiet as its gasoline counterpart, it doesn't smell like diesels of old, and it is efficient. Definitely get the diesel. –Paul Hagger
Not many full-size SUVs earn the "green machine" label. But the addition of Audi's 3.0-liter turbodiesel engine turns the Audi Q7 into a fuel-efficiency champ. Paired with an 8-speed Tiptronic automatic transmission and quattro all-wheel drive, the Q7 TDI is rated at 17 mpg city/25 mpg highway. In the real world, I saw close to 20/30. With such impressive fuel economy, you might expect the performance to be anemic. Wrong. The turbodiesel engine develops a ton of torque, and the 8-speed transmission keeps it in the power all the time. Acceleration is a little flat off the line, but once it's moving there's always power on tap. Vague steering and a soft ride had me initially wishing for a sport package, but I found the suspension tuning to be correct for this type of vehicle. Inside, the Q7 is first-class luxury all the way, and the Prestige package adds $12,000 of technology and luxury features. –Mike Meredith
The Q7 is no small SUV. It has room for seven people and plenty of cargo space, and it weights close to 3 tons. But with the diesel powerplant, Audi seems to hide the weight well. Acceleration is strong and smooth, and in city driving I saw about 22 mpg — that's about the same as my little Subaru Impreza. Being from Audi, the interior is nicely done and the seats are comfortable. The third row is not bad once you reach it; however, climbing in and out requires the skills of a contortionist. Diesel seems to be a great solution for all large SUVs — it makes such perfect sense — but the price could be prohibitive. The $5,000 premium Audi demands for the diesel may make it difficult to justify. –Perry Stern