There are 55 gallons in a drum and 42 gallons ( 1 U.S. gallon =

3.78541178 litres)

in a barrel (i.e. 1 Barrel = 158.9872948 litres). Originally there were 40 gallons to a barrel however, that was changed in the mid 19th century to give a little extra so consumers wouldn't feel "cheated".

A little over 23 gallons of gasoline can be refined from a barrel of oil. Other products (jet fuel, lubricants, etc.) make up the rest.

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My guess is you are far under estimating the potential revenues. When I get a chance I'll give it a test drive.

John