2008 ram Hemi, which tunes work with 91 gas

[corneileous]

I currently have 91 in the tank, running the 91 performance tune. Since gas is startin to get a little more expensive, I think I'd like to retune for 87, but I don't want to wait till my current tank is empty...lol. Don't quote me on this, it may be down to half tank but I don't remember.

Can I run the modified stock tune or MPG booster tune with 91 octane? If my memory serves me correctly, the three performance tunes had to use the octane fuel they were named after.

Thanks in advance.

[mikel]

you can tune for less octane than you have in the tank no problem, just cant go the other way

[corneileous]

Oh ok, so there won't be no adverse effect similar to that of running higher octane in a stock vehicle? I kinda figured that was the case but since this isnt factory tune were talkin about, i wanted to make sure....lol.

Thanks....

[corneileous]

So again, unlike the factory tune that retards the timing and all in the presence of hotter fuel so that everything stays the same as it was programmed to do so from the factory, will the MPG booster tune do this as well or will it let the computer adjust to and run accordingly to higher octane fuels if I choose to run them? I probably won't ever run anything over 87 while it's programmed to get me good mileage in the event of high-priced fuel since that's kinda the point of that particular tune in the first place is to save ya money and get better performance to boot over stock but, I would still like to know if I would be wasting money with premium like you would with no custom tune.

[mikel]

the pcm never adds timing to work with higher octane fuel, it will pull timing to work with poor fuel, but does not add.

[corneileous]

I guess I see kinda what you are saying but, what I was asking was, can I run any octane fuel on that MPG booster tune. In other words, if I were to run 89 in it, will it still back the timing off to 87 or will it run it with benefit on whatever grade of fuel I put in?

I just don't want it to be like factory programming where like, if you put premium in it and it's preprogrammed to run off 87, you won't get any added benefit from the premium fuel, that's all.