It's an EMPEEGEE thread, not an AITCHPEE thread!
For a given weight and drag CD there is a direct inter-relationship between fuel burned, gearing, revs, and mpg..>
Maybe not so common here in merikuh where gas is always so cheap but fairly commonly understood where the "normal" car is 1.3 or 1.6.
Many cases where a bigger engine beats a smaller in real world driving..The bigger one can be gear taller, and can be at lower rpm for a given speed..the smaller one to keep up with traffic needs to be revved higher all the time..and they're geared shorter...One that springs to mind is a Golf II with a 1800 had 3.7 or so final drive and the same car with a 1,3 (and that 1,3 was a bitchin-er-er motor than the 1,8 8v-----was geared stock at 4.47>.
The old MkII Escort did better mileage with a 2,0 Pinto than it did with a 1,8
I've built scores and scores of Saab 96 motors with 10,8 compression and a 2bb car with 38/38 carb that did better milage than the 8.0 comp 1bbl (34mm) carb---on long distance steady cruise or matched the poopy motor crusing at 55 when the nice motor was moving the car along at 75...
(around town blasting thru the gears and going up Seattles hills they did a little less but that because it was simply too much fun gassing it up and grabbing gears up up up.. but thats operator problems (I used to warn guys that MPG would suffer if they couldn't restrain themselves...none could) But cruise it make sense..to go 75 means 4166 rpm...One the low compression motor to make 4166 you had to open throttle this much....on the high comp motor you just had to crack it a little bit to make the same revs.
that hain't a hard concept...think of a typical turd 88 245 like that one sitting right in front of me about 12 feet.. choose say 45mph...It can do that in second at xxxx rpm, in 3rd at zzzz rpm, in 4th at yyyy rpm and 5th at #### rpm...What is the throttle setting for each of those? less and less as the gear goes up and the pedal does too. Same car, same engine les open throttle gets moar Em Pea Gees
Maybe I'm 'splaining it wrong...