If you put that question into Google, you get an answer saying turbo engines have better mpg, but I remember reading that, during the development of Ford’s 7.3L gasoline engine, they came up with some kind of formula that calculated the most fuel efficient engine for a medium duty vehicle was the N/A 7.3 they ended up with. I’ve also heard it from some of my engineer friends. So what is it?
Not really. If you match up cars with similar power figures and compare their fuel consumption it’s normally about even. You can’t make more power from nothing. A 400 hp V8 vs a 400 hp turbo 4 cylinder will do about 20 mpg in the real world. The gearing will make a difference and the driving style obviously so you need to also match the power output when cruising for example. It’s where the theory and the real world don’t really align. Everything has gone towards fewer cylinder counts these days but when you compare the fuel economy and the power output there isn’t much change. There are outliers though.