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This is not a scientific experiment, but.......
I just ran the same 10 miles of inter-city interstate at a cruise-contolled 65 mph. Ten miles in one direction, turned around and ten miles back. I re-set the "Avg Mpg" on the dash as I started both runs. The first run was with the auto trans in the "D" position, so it was in 5th gear. The return run I locked out 5th and ran it in 4th gear.
First run 10 miles @ 65mph (2000rpm in 5th) = 23.7MPG
Rtn run 10 miles @ 65mph (2300rpm in 4th) = 22.6MPG
So, in simple non-scientific terms, on this test at the same road speed, but differing engine speed (rpm) the lower rpm generated a fuel economy improvement of 9.5% (1.1mpg). Might not sound like much, but if you run a tank a week like I do, that equates to an additional 20.46 miles per tank @ $3.30 gal is close to $325/year in savings.
Granted, we don't buy Wranglers for good fuel economy, but I bring this up to simply show that even slight variables in engine speed can make a difference in fuel consumption; something else to consider when we start talking gear ratios and tire sizes. The 3.21 works great for me, and considering that I won't upgrade to anything bigger than a 33" (not much bigger than the stock 255s) I think I made the right choice FOR ME.
I just ran the same 10 miles of inter-city interstate at a cruise-contolled 65 mph. Ten miles in one direction, turned around and ten miles back. I re-set the "Avg Mpg" on the dash as I started both runs. The first run was with the auto trans in the "D" position, so it was in 5th gear. The return run I locked out 5th and ran it in 4th gear.
First run 10 miles @ 65mph (2000rpm in 5th) = 23.7MPG
Rtn run 10 miles @ 65mph (2300rpm in 4th) = 22.6MPG
So, in simple non-scientific terms, on this test at the same road speed, but differing engine speed (rpm) the lower rpm generated a fuel economy improvement of 9.5% (1.1mpg). Might not sound like much, but if you run a tank a week like I do, that equates to an additional 20.46 miles per tank @ $3.30 gal is close to $325/year in savings.
Granted, we don't buy Wranglers for good fuel economy, but I bring this up to simply show that even slight variables in engine speed can make a difference in fuel consumption; something else to consider when we start talking gear ratios and tire sizes. The 3.21 works great for me, and considering that I won't upgrade to anything bigger than a 33" (not much bigger than the stock 255s) I think I made the right choice FOR ME.