The fuel-mileage figures for Leg One of the Audi Mileage Marathon are out and the bar for Leg Two (the Chicago to Denver trip I'm on) is set high. Several teams managed to wring more than 28 mpg out of a 3.0L diesel-powered Q7, and more than 40 mpg out of the A4 with same engine. Two teams recorded about 36 mpg in the Q5, and the duo in the lone, 2.0L diesel A3 hit 45.3 mpg. Meeting or beating those figures -- specifically those of the Q7 -- will take some serious effort. But will it be worth it?

From the standpoint of the average Q7 diesel buyer, the answer is more than likely no. Few if any Q7 TDI shoppers will be resorting to tactics like drafting semis or sticking to 65 mph with the dedication of a Buddhist monk. Instead, they'll set the adaptive cruise control to 75-80 and forget about it until the nav tells them its time to exit and fuel up. On a drive as long as this one, the difference between 65 and 80 is about an hour and a half. Time, unlike fuel, can't be bought at the nearest Shell station. My partner for the trip, Jennifer Geiger of Consumer Guide, felt the same way. Conflict of interest avoided. Both of us agreed to drive our diesel chariot the way we'd drive any other car -- since that's how it will be driven by Audi's customers.

On trips of this length, misadventures are always a possibility. But they usually don't happen within the first mile or two. As pilots of Q7 No. 1, we were told to lead the caravan and follow the video car. Unfortunately, the video car was on a different wavelength from everyone else and chose to take what can be best described as the scenic route through downtown Chicago. Jennifer, a Windy City native, repeatedly expressed her concern that we were going in every possible direction except the right one. Once everyone got in sync and the journey to Memphis finally got going, the rest of the trip proceeded without a hitch. Several pit stops were made along the way, including lunch at the Depot Supper Club in Salem, Illinois. The closest we got to another misadventure was when Jennifer had an unexpected lunchtime encounter with a German TV crew that asked for her opinion as to why Americans don't like diesels.

On our route through Illinois, the seemingly endless horizon of cornfields was interrupted by the occasional curiously placed subdivision. Further south, there was a span of various trees replaced by more farmland. In Missouri, cotton replaced corn. Quite a difference from what I'm used to in Southern California. We also had several encounters throughout the day with folks curious about our heavily decaled SUV. One gentleman, who had spent some time in Europe, recognized the TDI acronym and proceeded to praise the oil burner. Several other people, including a friend with whom I spoke on the phone, posed the usual questions upon finding out we were driving a diesel: Is it loud? Does it smell? The answer of course is no. Those misconceptions are relics of a bygone era, but these encounters underscored the challenges that Audi and others face in getting the mainstream public on board.

Far from being loud and rough, the 3.0L V-6 is smooth, quiet, and plenty powerful. On the highway, it's impossible to tell that the Q7 is in fact a diesel until you put the pedal to the floor and it hustles forward without much fuss. On city streets, the engine note is just different enough to give it away as different than a gas-burning V-6. Besides the engine, the diesel Q7 is remarkably similar to our since-departed 2007 Audi Q7 long-termer which was powered by a 4.2L V-8. Though official prices won't be released until closer to the Q7 TDI's early 2009 launch, word on the street is the base price will be far less than the Q7 4.2's $60,000-plus asking price. Before options, of course.

As for the fuel economy, the figures won't be ready until Friday morning, shortly before our 22 car caravan heads out for Dallas, but rough calculations can be made. During the 480-mile trip from Chicago to a pre-designated gas station about 40 miles outside of Memphis, the Q7 went through only about three quarters of a tank -- an impressive range. Assuming the fuel tank in the Q7 3.0 TDI is the same 26.4 gallon tank as the gasoline Q7's, this results in a fuel consumption of about 19.8 gallons of fuel, resulting in a fuel economy of roughly 24.2 mpg. Slightly below Audi's claimed 25 mpg, but considering our average speed was probably somewhere north of 70 mph, it's not too shabby. It won't take much to get to 25 or 26 mpg. To put things into perspective, our V-8-powered long-termer averaged 14 mpg during its stay.