New Mercedes V-8 Increases Power, Efficiency

By Joe Bruzek  on July 22, 2011
A new Mercedes-Benz V-8 debuting in the 2012 SLK55 AMG later this year will be a prime example of having your cake and eating it too. Power is up significantly over the preceding V-8, and thanks to new gas-saving technologies, Mercedes says mileage increases by around 30% over the 2010 SLK55 AMG. That car returned mileage of 14/22 mpg city/highway.
The 5.5-liter V-8 has 60 more horsepower than the previous SLK55 AMG for a total of 415 hp. It’s similar to the 518-hp, twin-turbo V-8 found in the 2012 CLS63 AMG, but loses those turbochargers in favor of natural aspiration.
Cylinder deactivation and direct injection are two added features used to increase gas mileage on the new engine. Mercedes calls its cylinder deactivation "AMG Cylinder Management," though the feature is used elsewhere in the industry under different names. During light driving conditions, four of the eight cylinders are shut down by closing the valves and cutting the cylinders’ fuel and ignition supply. The feature in the SLK55 will only activate if the efficient Controlled Efficiency (C) driving mode is turned on by the driver.
A stop/start function like that found in the CLS63 AMG is paired with the 5.5-liter on the new SLK55 AMG. It automatically shuts off the engine when the car is stopped to save gas. The feature is most common in hybrids and rarer in non-hybrids. It’s especially rare in performance cars like the SLK55 and CLS63.

The SLK55 AMG with 5.5-liter V-8 debuts this September at the Frankfurt Motor Show.


Road Test Editor Joe Bruzek covers’s short-and long-term fleet of test cars and drives a 1998 Pontiac Firebird Trans Am.  Email Joe