Remove friction, tweak the compression, do a little this, do a little that.

@Matt I was talking about a specific subaru, with a turbo and 4cyl engine which had a similar power output and gas mileage as a heavier, and larger displacement vehicle

I mean...it seems to be working.

All things considiered the Subie is the worse of the two by that comparison, considering it's powering a car about 1k lbs lighter

Exactly

Both are AWD

But the Subaru has a higher thermal efficiency

Eh, but per the drivers, the Tahoe is less efficient on gas

Yeah, same same

http://www.fuelly.com/car/subaru/wrx_sti

http://www.fuelly.com/car/chevrolet/tahoe

Not by as sizeable margin as it should be tho, lol

Well that actually supports me bringing up thermal efficiency and fuel efficiency being quite different, and doesn't explain any misunderstanding on my part.

What?

No, it doesn't

Unless you tagged me instead of @LordCaledus by accident.

I'm the person who within the last few minutes said thermal efficiency is not fuel efficiency after he was using the terms as if they were interchangeable.

It's the difference between power/lbs of fuel, and miles/gal of fuel

I don't know what you think the misunderstanding was here, and it seems like you don't either since you can't express it.

The Subaru is more *efficient* with the displacement it has

Yes.

And it has a higher compression

From forced induction

Ok, why are you saying this stuff though?

I don't know what comment you think you're responding to at this point, but it wasn't one I made.

Look, higher compression will lead to higher power but that doesn't mean you will use less fuel, it just means the car will move easier

forced induction in general has traditionally lead to worse economy

It's worse economy per vehicle, because it has been used to INCREASE POWER.

because it forces more fuel in, which means you burn more in each detonation

I used the wankel as a good example, the Subaru engines work too.

Also, forced induction has often been used to allow for otherwise underpowered engines to be put into vehicles too heavy for the engines

Wankel me off.

I mean it would kind of depend on the strategy behind it wouldn't it?

again, this isn't going to help economy at all

@Fitzydog who are you thinking is disagreeing with this? You're making the same point I made when I came in here and saw it being used interchangeably with fuel economy.

No one used it interchangeably, we used it as a direct correlation

@LordCaledus was using it interchangeably, as well as using emissions and fuel economy interchangeably.

Also, you said compression has no effect on fuel efficiency

for the most part, yes, a high compression ratio will allow for more energy to be developed from each detonation, but a higher compression ratio will also often result in more fuel and air being pushed into a cylinder

What?

I mean, I didn't.