This sounds interesting. School just started up, so there's a daily commute there (4 days a week). The weekends, we maybe drive a mile a day. But I know I do a lot of stupid errands, like getting something from the grocery store the day after I was already there.
I want to say we get about 250 miles on a full tank of gas, and the most it's been topped off at was just under 12 gallons. We usually fill it every week and a half when it's around a 1/4-1/3 of a tank.
Campus is just under 10 miles away, times two is 20, times 4 is 80 miles. 80 divided by 250, is right around 3 weeks of going to and from school.
Well the AC is broken, so there's less wasted gas now, than there was before. That's one way to stretch the tank just a bit.