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Jonahs
I was thinking the same thing but, what got me to wonderng is in the economy mode it adjusts tranny shift rpm, firmness, rev limit and a few other things. It also of course set it at 87 octane, shrug. There were about 6 or 7 perameters it changed. It does try real hard to get into high gear real fast but, in turn it down shifts just as fast on little hill. That I guess is the reason he said use econ. on trips. I do not like it but, like to understand it as far as retarding timing which You helped there. If rig comes on 87 why tell You it is being set there? It really does not give much advice in the book as to how You should determine what You should do. When I picked it up I was told set it to economy on trips, rv/tow around town @ combined driving. Then there was the performance setting which i have been running it there as it really makes it run very good. I just can't keep my foot out of it. I can't wait to get SC or turbo. Even now at lights I'll end up beside a kid with a small car. I set there and then I hear an engine race, them. I just see the green and look at em in the mirror. I can not see How You guys with SC can stand it. My daughters keep saying You'll end up in the slammer.
Well thought I would add a little more info. It is just curious. I run 87 in perf. never get a ping. It does help power a little with higher octane but not noticable to get excited about.
Having colder thermo helps there as I had been doing it in My 5.3L Silverado for 150,000 miles and it still runs like I just bought it. Low oct., perf. setting in it. Keeping it as cool as possible helps stop preignition. It has electric fans etc. I'm going to GM electric fans next on H2, it can be programed to run the fans with OEM harness that let's You add a post to operate with computer. Set it at 180 degrees with 160 degree thermo should keep it cool. Has been very nice to Silverado so far. Anymore advice is welcomed.

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