I subscribed to this really nice site not long ago and i was really happy to track down all my fuel-ups! The calculation made are really neat and precise. However i noticed a small "lack" in this site, the Kilograms unit. I have a CNG converted car (methane) and, at least here in Italy, methane is sold in Kilograms and not Liters. In this site is just a "unit", nothing more, because calculation are anyway correct.
Anyway this site is really good and would be really amazing if more people participate to it!