I am betting the V8 will get better mileage than rated. Our brilliant gubment makes automatic subtractions based on displacement in their formula. Seems they could save everyone a lot of trouble if they just hit cruise control on a test track to determine mileage before the did the crash tests, at least then the numbers would be based on some actual data.
BTW, my 28mpg rated 99 got 30-31 highway with only a cat back.