It gets about the same as my '03 350Z when I'm putting the pedal to the metal.
Freeway cruising is interesting -- in 6th gear at 70 mph it's practically at idle rpm. At 100 mph in 6th, she's only turning 1,800 rpm. So, sedate highway cruising isn't too bad in the fuel department. The Viper only has an 18 gallon tank, which you can suck dry pretty quickly with the pedal to the floor.
Lol, and that 2003 of yours ain't no slouch. Is it.
So is the ASP getting lots of road time at the moment Tere?