This does come up a lot ... for ethanol production. How much fuel is used to produce ethanol is constantly discussed, with some people claiming it is barely break-even or even energy-negative.
But yeah, no one then goes on to give equivalent numbers for petroleum.
Always have to note that ethanol production from corn has dubious energy payoff. Switchgrass is definitely energy positive, but lacks a strong lobbying group to provoke similar investment and development.
But yeah, no one then goes on to give equivalent numbers for petroleum.