On the way back I had to get gas, so I did an experiment: noted mileage, filled gas to the brim, then did the same once I was back in the city, 30 miles and 0.536 gallons later... so just under 60 mpg.
If I did that ride daily, I guess I'd have to fill up once or twice a week, since I only have a 4 gallon tank (but "you need gas!" light turns on at 1 gallon remaining, which is only gauge). And I guess it'd then cost $3.50 - $4.00 per day in gas, round trip.
But the wind, man... holy shit. Throwing me all over the place.