Good question.
It (interweb) says NASCARs get between 2-5 mpg.
It also says the current 98-octane 260 GTX unleaded racing fuel now in use is to be replaced with Sunoco Green E15. I bet they love that. Why not make them take the wife and kids in the backseat?

And 360 million gallons-plus of gas is used daily in the U.S. That seems like a lot (considering I only fill my truck (24gal) maybe 4 times a year, excluding trips). I actually burn more gas in my bikes than the truck. Retirement is good; commuting sucks.