The M156/M159 loves octane - E85 ethanol versus 93 octane M156 W204 C63 AMG dyno tuning results
These results are courtesy of BrenTuning. There are two lines on the dynograph below, the dotted one for 93 octane and the solid line shows the same car on E85 ethanol. Both fuels were dyno tuned on a Dynapack hub dyno (attaches to the wheels). What is important to pay attention to here is not the peak figures but the delta. E85 is clearly allowing more timing throughout the entire rev range making substantial gains through the whole curve.
It would be interesting to see how the E85 results compare to say MS109 which is an unleaded race fuel. The M156/M159 being port-injected and naturally aspirated likely will not see quite the same gains with ethanol as a direct injected motor (due to the cooling effect of direct injection) but it goes to show that Ethanol works well with the M156 AMG motors.
Now if only someone would give E85 a shot with a supercharged setup...