Turbine fuel v's Avgas
Both have different calorific values, however they both produce a given amount of energy for a given weight of fuel, not volume. As 411A said, most piston engine aircraft displayed tank contents in gallons (US or IMP) or in litres, uplift in gallons or litres, measure fuel burn in gallons or litres per hour. To a point I agree with 411A in that fuel temperature did not play a big role in the piston airliners mentioned, however they were not subjected to the same extreme variations as modern jet aircraft. It does not matter whether you are flying a Cessna 150 or an Airbus A380, you will derive a given amount of energy (relative to engine type) from each pound or kilo of fuel you burn and this may or may not be the same volume depending upon temperature variation encountered. One method used to get maximum fuel on board is to uplift refrigerated fuel, i.e. same volume but more weight.