MPG and fuel capacity at 200 miles per hour

Its impossible to know what the average speed of the Corvette ZR1 during the chase scene yet it was mentioned that, after several minutes of film-time into the chase, it was going to be 75 to 80 minutes worth of driving before the ZR1 made it from point B to point C (we don't know how long it was from A to B). Frequently we saw the speedometer reach close to or exceed 200mph. The ZR1 has an 18 gallon tank with 21 MPG for hwy. Yet traveling at those kind of speeds drastically reduces the MPG. I recall an episode of Top Gear where the gents were taking an Lamborghini up to near 200mph and they said it would be a matter of minutes at such speeds that a full tank would be depleted. It stands to reason, I think, the Corvette would run out of gas long before it reached its final destination. Your thoughts?