There have been two reasons for complaints about hot fuel.
The fuel retailer buys truck loads with the volume compensated to 60°F. The quantity they pay for is the adjusted volume, not the actual volume at higher or lower temperature. The retailer also pays fuel tax based on compensated volume, not on the volume actually sold at retail. If the fuel is above 60° when sold, they'll charge more tax than they pay to the authorities and pocket the difference.
So...what is an adjusted gallon of fuel? It is 231 cubic inches of liquid at 60°F. If the temperature is lower, the volume will be less. If the temperature is higher the volume will be more. If the fuel is cold, below 60, you get more for your money. If the fuel is hot, you get less for your money. API publishes tables for the compensation of volume based on temperature and specific gravity of the fuel.
In actuality, the most accurate way to measure the energy content you receive is by weight. If fuel was sold by the pound, you'd get the most accurate accounting of the value of that fuel. There is some allowed variation in the specific gravity of fuels, and heavier fuels contain more energy. Measuring fuels by weight automatically compensates for temperature differences as well as specific gravity differences.
The fuel retailer buys truck loads with the volume compensated to 60°F. The quantity they pay for is the adjusted volume, not the actual volume at higher or lower temperature. The retailer also pays fuel tax based on compensated volume, not on the volume actually sold at retail. If the fuel is above 60° when sold, they'll charge more tax than they pay to the authorities and pocket the difference.
So...what is an adjusted gallon of fuel? It is 231 cubic inches of liquid at 60°F. If the temperature is lower, the volume will be less. If the temperature is higher the volume will be more. If the fuel is cold, below 60, you get more for your money. If the fuel is hot, you get less for your money. API publishes tables for the compensation of volume based on temperature and specific gravity of the fuel.
In actuality, the most accurate way to measure the energy content you receive is by weight. If fuel was sold by the pound, you'd get the most accurate accounting of the value of that fuel. There is some allowed variation in the specific gravity of fuels, and heavier fuels contain more energy. Measuring fuels by weight automatically compensates for temperature differences as well as specific gravity differences.
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