I've never got mine to single figures, lowest I've seen is about 16 I think, and that was trying hard. Never had it on a track though.8mpg? pah, the V6 does 6 when fully lit LOL!
the guys with the c63s I know struggle to get into the 20's though. I think I do too many miles to drive one of those as a daily driver. The new model is going to be a 4 litre V8, bet that will be pretty efficient. I have a feeling that's the engine Aston are going to use too, I believe they did a deal with AMG recently for engines.