Originally Posted by Mr_D
Here in WA state they are required to us a temperature compensating pump to fill any tank. So we always get an honest fill, but we also pay $2.89/gallon.
They do in Canada to at most big brand stations but I believe there is a limit to that adjustment, it adjusts for the difference in temperature up to 15 degree celcius.
Gas pumps work on a similar difference in that they compensate for the difference between the underground tank temp and the ambient temperature, also in regards to expansion of the fuel thats why they want you to stop the filling process when the pump nozzle kicks out the first time otherwise your tank could overflow if you let it sit for a while!