When I was a bit younger, I was on a dock and a guy came up to refuel his twin engine (big blocks) supercharged cigar boat. It was AMAZING! Only god knows what something like that costs but for some reason I felt the need to ask him, "Hey what kind of MPG do you get with that thing?" He said the words I will never forget.
"No idea. Because when you have a machine like this you do not worry about things like that" 