Also, correcting my previous comment, Pluto was 2" and 3" pipes, not 9".

That is, the vast majority of oil used in Allied operations in Europe passed through a set of 2- and 3-inch pipes, with 17 laid in total per the Wikipedia article I'd linked earlier.

Which speaks both to the flow-rates achieved (~400,000 Imperial gallons/day), and the energy content of petroleum.