Not every model has increased mpg numbers. In the case of the V6 SL 350, the engine output increased to 316 HP (up by 16 percent) but fuel mileage is 1.1 mpg higher, up to 28.5 mpg (Imperial, about 24 mpg U.S.). For the 8-cylinder SL 500 and the 12-cylinder SL 600, Mercedes has announced the same improvement.
For the SLK 350, the V6 increased the HP figures up to 305, while delivering 30.7 mpg (25 mpg U.S.), which is down 2.7 mpg. There's a SLK 200 Kompressor delivering the best mileage, 36.7 mpg (30.5 mpg U.S.) of the range. Then there's a larger SLK 280 good for 31.4 mpg (26 mpg U.S.) and the outrageous S55 AMG (they don't publicize the mileage figures for this one).
On to the CLC sport coupés (the 3-door hatchbacks). Europeans can get a CLC 200 CDI diesel able to run 48.7 mpg (40.5 mpg U.S.) which is 2.4 mpg more than the previous model. There's a small gasoline engine option as well, which will move the CLC 200 Kompressor 36.2 miles per gallon (30 mpg U.S.). This is 1.2 mpg better than before.
Last but not least, the CLS has improved consumption as well. There's a new direct-injection 350 GDi with piezo-electric injectors that gets 31 mpg (26 mpg U.S.), as well as a 350 CDI with respectable 37.2 mpg (31 mpg US). All CLS models are equipped with the 7G-TRONIC seven-speed automatic transmission as standard.
[Source: Mercedes UK]