Using the analogy of car engine size, if I have a V8 and am light on the gas, OR I have a V6 and am a bit heavier (but not heavy) on the gas (to get the same mild exceleration) then I will use more gas in the V8 than the V6 for the same route profile.
Basically, a V8 needs more energy just to turn over than a V6, but gives you more power when needed.
Strictly from a fuel point of view in aviation, is a bigger engine at lower thrust on an airplane as efficent as a less powerful engine at higher thrust? That seems to be what a few posts above suggest, but that seems hard to believe. If so, how does this depend on take off vs cruize?