I believe your acceleration experiment may be poorly designed (though I may be wrong since Jeeps may be more like trucks).

It is my understanding that car engines operate most efficiently usually somewhere between 3000 and 4000 rpms (for trucks, the sweet spot is usually between 1500 and 2500 rpms). Your most efficient speed, with little fuel and time trade off, should be somewhere between 50 and 80 mph. In your case, it looks like somewhere around 50 or 55 (loose guess based on your graphic). See what your RPMs are at that speed. Try keeping your RPMs near there when you accelerate (within reason consindering the conditions).

Also, try that just in first gear and compare it to idling. Measure your volume of fuel used and distance traveled. Measure over the same distance, starting from maximum idle speed in both cases. Do it again starting from a full stop.

Take a look at incremental fuel consumption over incremental speed.
0.062733333 0 to 45mph (this covers multiple gears, so doesn’t compare to other numbers)
0.0966 45 to 55 mph
0.121 55 to 65
0.1653 65 to 75

It looks like you still get a very slight increase in fuel consumption for an increase in speed then you’re down near 45 mph.

It would be cool to see narrower speed increments for the entire speed range of the gear.

I think it would also be good to note that this analysis ignores any time and traffic considerations. It is only relevant in conditions where you are the only vehicle on the road (your might be able so save fuel yourself, but at a cost of more fuel consumption for others).

If you really want to save fuel and still drive, stay in first gear at about 3400 RPMs and avoid stopping.