Quote Originally Posted by 89Vette View Post
BTW...Are you certain the cam's are the same? Even within SBC's their can be cam differences which would account for rating's differences.

I'd be surprised if Isuzu left any timing on the table. OTOH, raising PE from 25% to 50-60% could be worth 1-2mpgs.
Agree. For our job#1 truck to go from 3.2 SOHC N/A to 3.5 DOHC supercharged, gain a rooftop tent windsock and STILL return nearly 3 litres/100 better economy says that the 'power under the curve' of the SC is a major factor.
Cams here are very mild. I have heard that the cams in the Axiom are better, but only hearsay nothing conclusive. We never got Axioms here anyway

I'd be a good 2wd/4wd switching system (or even gear box) would make as much or more difference. (maybe combine the two?) FWIW, any Jeep I've ever seen rated (and/or owned) did much better in 2WD vs 4WD mode. I could feel a difference in power as well. Just seems to be way less drivetrain loss.

Look at the difference in the 2wd vs 4wd Ford Escape's MPGs. Fairly significant in my book. (I wonder if there's any other changes in gearing, etc between these.)
None of ours are TOD, so are always 2WD unless selected. For fuel range calcs off-road I always use 25l/100 (10 mpg) - long way between fuel pumps in Outback Australia!