A foot of concrete is a pretty good insulator too
.
I still reckon there isnt much difference to temperature of the tanks on a normal day. Maybe in the middle of summer when its 30-40 degrees.... but for most of the year I seriously doubt the 50-60L you pump will change much based on a temperature.
I guessing in the space of a day not much temp diff.
How much does the average swimming pool increase in temp during the day? sure the heat capacity of water is a lot higher and there is much more water in the average pool than a service station tank, but the pool is exposed to the hot air on the top layer too.
Though how much are we talking about in the expansion of petrol, its ~1ml/L/C
So for a 70L tank and a 4C temp increase we have, 70L x 4 x 1 = 280mls, so ~35 cents. Possilby there is something to think about, but more to do with not filling the tank with 15C petrol and parking it in the sun on a stinking day!
What temp is the gallon meant to be calculated at? The Americans do it at 16C, possibly we are the same, but would we ever be getting the correct amount in this country?
Interestingly Americans saw red on the issue:
Automatic Temp. Compensation, however, Canada decided to temp compensate their pumps as possibly the operators lost money due to the petrol shrinking over there!
studies in this country suggest we will never see temp compensation at our pumps:
CMIS Research - Operations Research - Petrol Temperature Study