We went on a 450 mile drive last week to the Sierras. The overall average was an indicated 23.5 mpg on my tuned 2014 HSE. Not bad considering the cruise control was on 74 and the trip crossed over the 7500' summit. On the way home I refilled the tank and calculated exactly 20 mpg. This is pretty much in line with other mpg calculations that I have made. I can see RR wanting their owners to feel good about their cars and seeing a somewhat optimistic mpg reading on the dash by maybe 1 or 2 mpg, but this is somewhat excessive. Why even have the thing if it is close to 20% off? Not a big deal but an observation.