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

Its not always the case this happens, on some cars, the smaller engines are no better for fuel economy then the larger ones.

I remember years ago, my dad had a 1.8 honda civic, and when it was in for service got given a 1.4, the car was basically the same weight, but the 1.4 was worse for economy then his 1.8 was. The cars themselves where a very similar weight, but the 1.4 had to work harder then the 1.8 did to travel at the same speeds, and therefore used more fuel.

From this I learnt to never buy the smallest engine in a particular car as the economy from a larger engine would be better.