I've had my F36 428 GC for a couple of days, gas mileage has been significantly reduced and considerably lower than the rating. I am coming from a 201hp turbo 4 cyl so I know what I should expect more or less. My driving style hasnt changed, I was always a pretty aggressive driver so I definitely havent become more conservative or demanding of the car.
I have two theories, 1 the dealership possibly filled the car with lower grade gas. 2, the car could be experiencing some break-in period where the gas mileage is lower.
I filled up the car last night and it seems more responsive and stable, and I'm averaging 15MPG.
