I agree with the comment about modern diesels. I am heartened to see that larger, more powerful diesel engines are being offered for larger cars in addition to the smaller ones that have been on the market for many years. Audi offers a 4.2l turbo V8 diesel in the A8 that delivers 345 hp and 590 fp of torque, yet a thusly equipped A8 with all-wheel drive gets ~22 mpg. This, in a vehicle that does 0-60 in under six seconds.
Audi already offers the A3 and Q7 with diesels in America, and will soon be offering them in A6, A8 and Q5. Their 2.0l four cylinder and 3.0l V6 diesel engines are already available here. It is not clear whether Audi intends to produce a version of the 4.2l V8 turbo diesel for the American market.
VERY Impressive fuel economy for such big and powerful cars
I'd bet it actually gets better mileage then stated. I drove a V12 760Li from Los Angeles to Ordieville last summer and we got about 24 mpg, quite a bit higher than the 19mpg that BMW pegged it at, which is pretty impressive for a 17 foot 5,000 pound V-12