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

To some extent, you can. But either way, you’re carrying around all that extra engine. 

If you took a fuel efficient car and put 500 pounds of “unused engine” in the trunk, you’re going to get worse fuel efficiency.