2011 Ford Mustang V6 rated 31 mpg highway

[101lifts2]

Originally Posted by Homeslice

Well I'm not a physics major, but if you take 2 engines with the same displacement but different HP, I don't see how more horsepower ALWAYS means less fuel economy UNLESS someone is actually taking advantage of it by accelerating harder. And I doubt the EPA test is doing that, does it?

Personally I think the increased weight of today's vehicles is more to blame.

You are forgetting about emission output. The lower the NOx requirement, the more EGR dillution and less power. Also, if you have to heat the cat up faster, more fuel. Plus cars are heavier today then in 1980s.