LAS VEGAS (KLAS) — With NASCAR coming to Las Vegas this weekend and gasoline prices climbing, do you wonder how much fuel a race car uses in one of those 500 lap endurance tests?

A stock car will use 100 gallons in a typical 500-mile race, according to Sunday’s South Point 400 at Las Vegas Motor Speedway is a 400-mile event. So, for that distance, figure each car using about 80 gallons.

Yes, the math works out to about 5 mpg of fuel. And you’re still miffed you can’t bet better than 18 mpg on the family SUV, right?

The racing fuel is a high-octane blend made exclusively for NASCAR by Sunoco called Green E-15. It’s 15% ethanol and unleaded gasoline with a greenish hue, which explains the name, and an octane rating of 98. (High-octane gas at the local pump is 91 and 93 in the Eastern United States).

Fuel tanks are 18 gallons, but they’re not always topped off. Especially at the end of a race, when crews are looking for every edge. Why? A full tank weighs more, so a heavier car won’t be as fast.