The Idea!!!!

doogievlg said

Sometimes the bigger motor improved mpg. I know it doesn't make since at first but I had a 94 ranger with a 4.0 v6. My roommate had a 94 with the 4 banger. I averaged five more mpg then him. Both trucks were standards and mine actually had the back seats as where his was a single cab. I attributed this to my motor not having to work nearly as hard as his to get the job done. It may have been something else but that's just my .02

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4 cylinders usually have deeper gears so they turn more rpm for any given speed.
Say a 2l has twice the gearing as 4l they would consume about the same fuel and air.
Also hp at speed is another factor say at 60 mph the 2l turns 3000 rpm and makes 100 hp
And the 4l turns 2000 rpm and also makes 100 hp they would both burn about the same mpg
Cause it takes about the same amount fuel and air to make 100hp.
Obviously I left out engine efficiencies in these examples.

And when I asked about performance I was talking reasonable power level for driving style.
I hate gutless cars and find they burn more fuel cause I push them harder like the 4 cylinders vs v6 above.
With the 273 you could easily build a 200 hp plus engine which is a decent amount of power and probably only lose a couple mpg if any over a slant 6. And the average car only needs about 50 hp to push it to highway speeds so anything above that is technically a performance engine.