The Audi A6 ranges between peppy and frugal to brutal and thirsty; it just depends on how much power you want under the hood.
For the best numbers of the lineup, look no further than the A6 TDI, new this year and on deck with 24/38 mpg EPA ratings, or 29 mpg combined. That should more than offset the S6's 17/27 mpg, or 20 mpg combined, given Audi's ambition for turbodiesel sales.
Gas mileage isn't too bad with the 3.0T and quattro. The supercharged, direct-injected V-6 powerplant and its standard all-wheel drive deliver 18/27-mpg fuel economy, or 22 mpg combined.
With the 2.0T, the A6 earns its best gas mileage ratings. The catch? To get those 25/33-mpg figures, you'll have to put up with a continuously variable transmission, a gearbox that seems out of tune with Audi's luxury niche. That's true just for front-drive models; with the all-wheel-drive turbo four, the transmission's an eight-speed automatic, and fuel economy registers at 20/29 mpg or 23 mpg combined.