The new Mercedes-Benz S350 BlueTec sedan may well offer the best value of any model in the automaker's lineup of S-Class luxury cars. Powered by a sophisticated V6 diesel engine, the S350 is only a tad more expensive than the S400 Hybrid, and significantly cheaper than the gasoline-powered S550, Mercedes's flagship luxury sedan. It's also rated to get 31 miles per gallon on the highway, and 25 mpg on average—which is 8 mpg more than the S550 and 4 mpg more than the S400 Hybrid. In other respects, the S350 BlueTec is identical to the S550, with the same roomy, elegantly appointed interior, spacious trunk, and sound-deadened cabin. The S350 BlueTec lacks the raw speed of the S550, but it's probably quick enough for most owners.