With seven distinct drivetrains in its portfolio, the Mercedes-Benz S-Class offers fuel economy that ranges from the ultra-efficient to the dismally delightful.
The greenest editions are the turbodiesel S350 BlueTEC and S400 Hybrid. The diesel edition, a new powertrain for U.S. buyers in this generation of S-Class this year, offers up EPA ratings of 21/31 mpg, the highest highway ratings of the entire lineup. Not far behind is the S400 Hybrid, with its lithium-ion battery pack and V-6 gas engine pairing; it's rated at 19/25 mpg.
The new twin-turbo, 4.7-liter V-8 engine available in the mainstream, executive-edition S550 achieves excellent fuel economy in a vehicle the size of the S-Class. Officially rated at 15/25 mpg in the rear-drive S550 and at 15/24 mpg in the S550 with all-wheel drive, it's capable of more. We've clocked an indicated 25.5 mpg on a 300-mile interstate trip where speeds averaged nearly 80 mph.
As you dip more deeply into the performance end of the range, the numbers fall precipitously. The S63 AMG fares best, its twin-turbo 5.5-liter V-8 putting down EPA ratings of 15/23 mpg. The twin-turbo V-12 cars are on another planet entirely, probably more due to their outdated five-speed automatic transmissions than anything: the S600 and the S63 AMG both are pegged by the EPA at 12/19 mpg, just a highway mile per gallon better than a Jeep Grand Cherokee SRT8--though the S65 is, at 4.2 seconds to 60 mph, a few ticks faster, too.On the bright side, the S-Class models do score pretty well for smog-forming emissions; despite its low mileage, the S65 earns a 6 out of 10 on the EPA Air Pollution Score.