Posted by moss6 on January 17, 03 at 18:39:31:
In Reply to: Re: 4.10 rear to 3.73 or 3.42? would it greatly improve gas mileage with 8.1l? posted by AJ on January 17, 03 at 04:20:59:
: Hypertech's Programmer III gives you the option for either 93 or 87 octane. I've tried both settings, and imrovements over stock were evident; 93 a bit better. Had a Hypertech chip in my '94 1500 Sub, with noticeable improvements, too. May not be the best thing available, but it's convenient, easy to install, especially if you don't have a competent tuning shop nearby.
: I've favored 93 for a couple of reasons. First, the engine can run slightly more agressive timing, that slightly improves performance. Not a big deal, but it makes me feel better. Second, I used to run 3 15-passenger vanpools, and after about 400,000 combined miles, I found 93 octane improved mileage about 6-8% over 87 octane. But, now that 93 is more than 8% more expensive than 87, its no longer a cost effective argument. Lastly, I've always felt 93 had "cleaner" properties, that might help an engine's longevity. I don't know for sure, but it may be contributing to my engine's lack of piston slap (so far..).
: Like I said, it makes me feel better. I run 87 in the sole vanpool I run now, but my "baby" gets 93.
: : Joe,
: : From reading enumerous posts on mileage claims from 8.1 owner's for nearly two years now I would say that the vehicals geared 4.10 are on a par mileage wise with the 3.73's and possibly even have a mileage advantage. You state that you are getting 10mpg in town, we are geared 3.73 with our 2001 8.1 and have always hovered around the 9 mpg mark in town until I had Wester's Garage reprogram the PCM. We now are always above the 10mpg mark in town but I wonder if it wouldn't be better with the 4.10's.
: : Now on the highway at 75mph the mileage was always in the 15mpg range if the wind wasn't a factor, sorry but I haven't had the opportunity to check highway mileage since Wester's did the reprograming, highway mileage is probably in the advantage of the 3.73 but not by a substantial amount.
: : A note for Bob:
: : If you use a competent PCM programer (not chip) there is no need to use fuel with an octane rating that is higher than 86.
: : Randy