DB, if you run like we did, you'll turn about a 4min lap. With 60 laps, thats 4 hours. Two pit stops = 3 driving segments for your 3 drivers. That's 1hr and 20min each. Your engine will burn about 20-22 gallons/hr. That means you'll burn somewhere around 26.5 to 29.5 per driving segment. 30 gallons is really cutting it close.