Why do larger engines get less MPG? Couldn’t a V8 be geared to a lower RPM and consume the same or less than an I4 at a given speed?

Question

I imagine some of the difference is due to weight (larger engines being in trucks) or performance (sports cars made to accelerate rather than cruise well), but it seems that almost without fail the bigger the engine the less MPG, I don’t understand where the extra energy goes if not to the wheels

In: Engineering

Answer 1

It also depends on the weight of the vehicle and the transmission. For example, my wife’s 2008 Ford Edge has a V6 with a 6spd auto transmission and weighs 5300 lbs. My 2005 Mercury Grand Marquis has a V8 with a 4spd automatic transmission and weighs 4100 lbs. My MGM gets better MPG than the Edge.