I weigh in at 340#, and run a Robin/Suburu 35cc GEBE. My tank is full at 16oz, and that will take me about 18 mi. around here in Indianapolis. Mostly flat, but a few gradual hills, and a lot of wind. I'm running the standard street gear, and get 30-31 mph on flat ground with no wind, if she's in a good mood..lol. I average about 17mph, (or that's what my bike comp tells me..lol). I believe that's around 144 miles per gallon of premium grade gasoline. Again...that's not half bad for a dude weighing in at 340.