That's true. There was a project engine back then by some amateurs working in the back yard under a shade tree who put some high performance parts on a stock engine. Things like a high flow polished intake manifold with a 4 barrel carb, high lift advanced spark cam, shaved heads, low constriction exhaust manifold, and got something like 30% increased gas mileage [with a light touch on the gas pedal] along with the expected power increase and of course lowered emissions.
This because the "oil boys" talk with "car boys" to determine Fleet MPG as a factor of fraction flow & output demand at the refinery.
Always have, always will, I reckon until enough of the curtain is pulled back so enough of the public sees how silly everything about this situation really is.
There's no mystery to us carnival workers, we see the show for what it really is.