Mileage figures have little to do w/ max power. That mileage figure is roughly using the same actual power, which is a relative sip of fuel.
The main difference would be in testing EPA methodology which which would be a bit more stringent/realistic to world use. On top of that, there likely is more rolling resistance at lower speed due to larger tires and heavier weight, offset somewhat by lower C/D at speed.
Basically it's hard to extrapolate ICE efficiency gains... they're there are sure, but probably in the single or low double digits.
I don't understand why they can't just build a basic pickup truck any more.
We had an old pre-fuel injected pickup. It had a bigger bed than the current truck, and seated six instead of five. It got 33% more miles to the gallon. The new one's transmission likes to overheat, even when not towing.
I have a 2015 Colorado with a 6 speed manual, long bed, 4.10 read end, and the 2.5L 200Hp four cylinder. Probably as basic as you can get, and nobody buys them, because for like 2k more you can get a v6 and fancy electronics.
The laws if physics don't owe us a free lunch. Light, safe and cheap powersource does not exist
Fossil fuels aren't a power source, they wre a power store - that power was collected and millions of years ago.
Also 100% productivity on 25 years is quite good - what did combustion engines improve in that time, 5%?