Since I raced the Mach 1, I looked up the specs for both rides. This is some numbers on a 2002 GTP coupe. Gives some mileage for those that always ask. Those numbers seem way higher than I thought they would be and gives HP/TQ.
P.S. Just did some calculations, that 315 in the city is if you use the full 17.5 gallons of gas to the last drop, same for the Highway!!!
Specs

That mileage seems pretty dead on to me.

But most won't experience the 315/490 ready out because usually they will only use about 15.5-16 gals most before they figure all the gauges saying "Low fuel" means you need gas. So It is kind of like a misconception, believing you should be getting that, but only if you run the tank dry and under perfect conditions.

Yeah thats if you run it dry. We probably have about 50 miles left till way say "oh crap!" at the gauge. Seems right, though.