You cant get free power, it all has to come from the fuel.
You must look at the LOAD ,, my car produces more power at larger throttle openings when TOWING at 55mph than when it isn’t towing at the same 55mph (or add any other load you want ,, windows open , car loaded with lots of weight..) ... smaller throttle opening , SAME RPM , different power levels (despite same RPM and same engine/car etc.) and LOWER fuel consumption ... the same can be said of different engines in the same chassis ... you have some cars where the engine is too small/overworked and it uses more fuel than the larger optional engine.
Your THEORETICAL info is good in theory ,, and is repeatable on a dyno as you simply run WOT against a big load and measure fuel flow and power output but in the REAL WORLD where PART THROTTLE is the NORM , results will vary considerably. You can’t take simple minded “most efficient at WOT” thinking into a “I just need 15 of those 300 available horsepower” to maintain a 60mph cruise world and expect them to correlate.
“Your THEORETICAL info is good in theory”
The only “THEORETICAL info” I stated was that you can’t get free power, it all comes from the fuel.
Not sure where there is any wiggle room there.
Blanket statements that big old cars use less gas than smaller new cars are silly. Of course, the whole “Cars were better in the 60s” thing is silly too. But every car thread gets pasted with those same tired old silly posts.
They don’t build ‘em like they used to. And it’s a good thing they don’t.
Styling is a whole different issue. Cars look so much alike today because of Government regulations that dictate so many parameters of a cars design that it is a miracle they aren’t identical in every way.
I think a lot of the “old cars are better” thing is because people long for the old styles (I liked the looks of the older cars too) and they long for the OLD DAYS. But that doesn’t change reality.
And reality is that a big old Caprice, or a Newport, or a Galaxie from the 60s was NOT built as well as today’s cars, and it was NOT safer, and it was NOT getting 20 MPG.