The Audi A8 made its name long ago for its aluminum space frame. It shaves some weight, which helps give the big Audi a gas-mileage edge over its rivals, even before it launches a new turbodiesel A8 TDI for the 2014 model year.
For 2013, the A8 gains a trio of new powerplants, each one more efficient than the one it replaces. There's a supercharged 3.0-liter V-6 with stop/start, and a twin-turbo V-8 with cylinder deactivation; both are paired with an eight-speed automatic transmission.
Thanks to the combined technologies across the lineup, those versions of the A8 achieve some impressive EPA ratings. The 3.0T sets the tone: it's pegged at 18 mpg city, 28 mpg highway, and 21 mpg combined, better overall than the BMW ActiveHybrid 750Li. Both the V-8s aren't far behind, whether in 420-hp standard output or the 520-hp S8 tune. The short-wheelbase V-8s are rated at 17/28 mpg, or 21 mpg combined; with the long wheelbase, the A8 checks in at 16/26 mpg, or 19 mpg combined.
It's only with the 500-hp W-12 engine where the fuel-economy numbers take a nose dive. In its sole configuration, as a long-wheelbase model, the A8 L W12 is rated at 13/21 mpg, or 16 mpg combined, figures we'd associate with a large luxury SUV at first glance. That's why you'll see a $2,100 gas-guzzler tariff applied to its sticker, on top of its $134,500 base price.