Interesting: I just looked up the Corvette Z06's fuel EPA economy rating:
Model 1 Vehicle Characteristics
It's
15 mpg (US) city /
24 mpg (US) highway /
18 mpg (US) combined
No wonder the British guy was able to win his competition on % over the government rating.
Extend the graph, and this car "meets" its EPA highway rating at 130+ km/h / 80+ mph! (Steady state, level road, etc.)
That's astounding. In stock form, my car's "EPA highway" speed was below 100 km/h / 60 mph.