The Audi Q7 TDI is a seven-passenger luxury crossover that is greener and more efficient than its VW and Mercedes Benz counterparts. Audi dubs it the world’s “Cleanest Diesel SUV.”

Audi supports that claim with the Q7’s ULEV-II (ultra-low emission) certification standard. With help from its advanced exhaust emission control system and urea-based treatment system, the Q7 produces 25 percent fewer greenhouse gases then vehicles with comparable gas engines.

Powered by a 3.0-liter diesel engine, the Q7 rates at 225 horsepower, and 406 pound-feet of torque. As with most diesels, it offers a lot of low-end power, good for both acceleration and towing capacity.

In terms of mileage, the EPA gives the Q7 a modest 17 city and 25 highway, but unlike many gas-powered vehicles that fail to meet the mark in real-world conditions, these numbers are accurate, if not low. During last fall’s Audi Mileage Marathon, one driver got more than 33 miles per gallon from the Q7, and many participants topped 30 miles per gallon. Not bad for a 4,500-pound vehicle.

Real-World Mileage Loop

We took the Q7 out on our usual twice-around 112-mile mixed route to see for ourselves. The first test drive was not quite hypermiling, but it was very conservative in driving style. We stayed under the speed limit and feathered the accelerator. On this loop, we beat the EPA, turning in 29.8 miles per gallon.

On our second, more aggressive run—left-lane driving, hard acceleration, and frequent passing—our Q7 gave us 20.6 miles per gallon.

The test confirmed that the Q7 TDI’s powertrain is about 30 percent more efficient than gas-powered engines of similar size, and allows an interstate cruising range of more than 600 miles on a single tank of gas. To further boost fuel economy, the Q7 wears low-rolling resistance tires with a narrower tread than conventional all-seasons.

The Q7 drove like a charm—fast, powerful, smooth, and agile. And thanks to its diesel characteristics, off the line performance was far superior to a comparable gas-powered vehicle. We are hard pressed to find something to complain about with the driving experience—although some reviewers have complained of a “heavy feeling.”

Aesthetically, the Audi Q7 TDI shares the same beautiful lines as its non-diesel sibling. Aside from the badging, it looks virtually identical. And the same goes for the interior. The cabin is refined and plush with amenities. There’s everything from 12-way power leather seats with heat to Audi’s impressive multi-media interface system. The interior beauty, such as the decorative wood inlays, matches the sharp exterior design.

The performance and elegance comes at a price. The base sticker for the 2010 model remains at $50,900—but piling on the options will quickly put the Q7 over the $60,000 mark. However, buyers will get some relief in the form of a $1,150 Alternative Motor Vehicle Credit from the IRS.