Automotive Gasoline Tanks - Rated Capacity - Tolerance

I would be surprised if there are any "standards". Probably the best source for data would be Consumers Union. I don't recall if they measure fuel tank capacity and compare it against the stated capacity when they test and rate automobiles. They certainly do it for refrigerators and commonly find the stated capacity to be much higher than the real. -jmm

If a tank is filled up completely to the proverbial 'gunwales' and the lid put tight on then there is a risk of rupture due to the different rates of volumetric expansion of the materials of construction of the tank and the material it contains!

Oversize the tank by 5-10% as a margin of safety. Or, alternatively, underfill it by 5-10%.

Gasoline and other fuels are dispensed by appliances that have flow totalisers that are traceable to international volume standards by calibration. In the UK the local Weights and Measures section will assess fuel pumps at intervals for accuracy.