How about crowdsourcing for people who want and gather the stats if they don't to generalize. When the Ignition changes and there is a change in Fuel Level Input (if supported) grab the location, popup a dialog box asking if you filled up (yes/no), fuel grade, how much (gallons/liters), what was the price in a numeric pad for price and volume. Optional is fuel offered at a discount? If so, how much at your fuel grade. Boom! you have crowd sourced fuel data that you can sell to others.