Sorry, but I do. It has a lot to do with powerband and gearing, as well as the vehicle’s fuel map. At 2200rpm, the fuel map just sucks because the air metering device isn’t really all that accurate. At 3000rpm, it’s much better and more efficient.
You do realize that the *most* efficient mode of use for a piston engine, in terms of power per fuel unit consumed, is wide-open-throttle, right?
What I do know is that my 5.9 litre engine obtains a fuel economy of approximately 21 miles per gallon at 55 miles per hour and less than 15 miles per gallon at 70 miles per hour. Since this is what I drive, I drive accordingly. When I am in a posted 55 I drive 55. When I’m in a posted 65 I drive 60. When in a posted 70 I drive around 60. I’m not in such a hurry as everyone else is I guess.
By the way, my vehicle does not drive at 2200 rpms at 65mph. It’s more like 1800. Maybe you need to recalibrate your gearing or something.
Absolutely correct. Until you put it on the road and make it fight drag. Drag is an exponential force, and once you cross a certain threshold (around 25mph) differences in engine efficiency become less important than the drag coeffecient. At speeds over 50mph, there is just no comparison. Drag is a full on force draining 95% of your fuel. At speeds over 100mph, the tiny amount of fuel that's expended on inertia, internal and external friction combined is 2 or more decimal places to the right. It's completely inconsequential.