Filling stations nowadays all have Veeder-Root tank monitoring systems. If you were so inclined, you can request a printout from the monitor. It only takes 15 seconds for the computer to print it. Problem is that they only give temperature, and water level in the tanks. I've seen some tickets that show 10-13" of water in the base of the tank.TThat's like 300-500 GALLONS of water, just sitting on there with the gas. Stay away from pump gas for your bikes, you're begging for problems...

Unfortunately, as of about 6 years ago, the tank probes were not set up to distinguish gas/eth percentage.