You also have to factor in (at least for trips) the real total time it takes to fill up. Typically you turn off the interstate and drive a mile or so into town, find the gas station, pull in, fill up (where you have to be at the pump while filling), then you may make a pit stop / grab a snack, and generally stretch you legs (assuming you've been driving for 400 miles = 7 hours). Whereas the Tesla quick charge stations, I believe you can leave your car unattended while it is charging.