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Discussion Starter · #1 ·
I've never really known how much difference there really was between one or two Octanes. I put an 87 tune in my 05 Ram but I always run 89 Octane in it. I know that you're not supposed to run lower Octane than the tune, but will it really hurt to run 89 on a 91 tune? I really want to run it, and i might for a short while, can anybody tell me what to look for if I do decide to run it and the Octane difference does cause a problem?
 

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Discussion Starter · #4 ·
Ya, I knew that it advances the timing, just wasn't sure if 2 Octane difference would be enough to make a difference or not. Probably better just stay away from that and avoid some major issues not far down the road I guess. I've been considering running 93 through it anyway. I did some simple math and it looks like if I can get just one more MPG out of it average it'll pay for itself... Probably a better route.
 

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It will also pull timing out to keep it from detonating, preventing the performance you would gain from running 91 octane on the 91 tune.
Agreed!.........
 

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^like they said, you have knock sensors so it should be fine, you'll just not be getting the full performance benefit.

Are you 2wd, reg cab, short bed? If you have a lighter truck you'd probably be fine...the less load you have (less weight) the less likely to detonate.
 

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Why would you run 89 on a 91 tune? The ONLY reason I could see for this is you are at high altitude... If you arent, and they sell 91 in your area, you are just being a cheap ass and should return your tuner. If 10-20 cents breaks the bank, then you probably shouldnt be messing with your vehicle at all.
 

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doz no need to be harsh on him. Some people don't know the differences in octane and the effects it can have on an engine. He posted this as a question asking for assistance not to be put down and abused.

Now....

I recommend running 93 through it a little to bring the all around octane level up in your system to closer to 91. Cycle a tank or two of 93 through and then run 91. After that then install the tune. I cycled mine through like this and installed the 91 tune with the speed limiter at 160 and the throttle gain at 13.5% and believe me is it a nice run. Will soon be changing my shift points though to see how that runs it out. If you don't understand something on the tuner then best to leave it alone and ask someone on here or have the manufacturer explain/do it for you.
 

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Not meaning to put him down but seriously, theres a reason its tuned to a certain octane. Even if he doesnt understand WHY he needs to run it, he should understand that its meant to run what its tuned for.

As for noticing a difference, you wont just as stated. Your engine will pull timing once knock is detected and youll never know about it. Its definitely not good for the engine though and its counter-productive. Why hurt the motor over a few pennies for negligible performance gain?
 

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Discussion Starter · #12 ·
I'm running the 87 tune on it now. I simply asked to see if there is maybe a margin that somebody else has found. I understand that they say not to run any less than 91 in a 91 tune etc, but I also know that a lot of companies will say this type of thing to cover their a$$ if something does happen. I do understand timing and how it affects the engine, what does it hurt to ask if someone else has already tried it and had no issues? I have been debating between running the 93 through to up the avg. octane in the tank so I can run it because no, 91 is NOT available in my area, and 93 is very hard to find. I have one gas station in a 35 mile radius that will sell 93, so thanks Doz for the harsh words, very appreciated. I'm simply going through ideas. I've done a lot of carburetor work, but I'm new to tuners, heaven forbid there be a learning curve. I knew before typing in the question that I'd probably get a long list of no's with the occasional wtf, but now atleast I know for sure, I've been surprised before...
 

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Discussion Starter · #13 ·
And Snrusnack, it's a 4wd, quad cab, short box, with slightly taller tires, not exactly a light truck. Thanks for the help guys.
 

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I'm running the 87 tune on it now. I simply asked to see if there is maybe a margin that somebody else has found. I understand that they say not to run any less than 91 in a 91 tune etc, but I also know that a lot of companies will say this type of thing to cover their a$$ if something does happen. I do understand timing and how it affects the engine, what does it hurt to ask if someone else has already tried it and had no issues? I have been debating between running the 93 through to up the avg. octane in the tank so I can run it because no, 91 is NOT available in my area, and 93 is very hard to find. I have one gas station in a 35 mile radius that will sell 93, so thanks Doz for the harsh words, very appreciated. I'm simply going through ideas. I've done a lot of carburetor work, but I'm new to tuners, heaven forbid there be a learning curve. I knew before typing in the question that I'd probably get a long list of no's with the occasional wtf, but now atleast I know for sure, I've been surprised before...
Be sad and take it how you want. You said yourself that you understand what octane is and how an engine works so why would it be different with a tuner? Knock is present whether its carb'ed or FI, forced induction or n/a. Its just frustrating to me that people want to spend $300+ dollars on a tuner and get a performance upgrade just to try and be cheap and ask if they can "get away" with running a lower octane.

If you did your research, youd know that most tuners have data logging. If you are unsure if you can run 89 on a 91 tune, data log as thats what its there for. See for yourself if its pulling timing due to detonation. You purchased a product that will answer your question.

Call it harsh if you want, but its reality. Too many people jumping into something they obviously know nothing about without doing their research. You can find GOBS of information between here and other sites about the question you asked. You are spending hundreds, if not thousands of dollars modifying your truck and you are trying to save $.10/gallon on fuel which could potentially harm your engine and negate the money you just spent for performance modification. You are basically willing to hurt your performance and/or engine for $100/year difference in fuel cost. Seriously??? Yeah, harsh reality, deal with it ;/ Maybe you shouldve opted for a Prius.
 

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I have a question on this. I understand everything stated already, but I travel often and if I were to need to fill up and the best available was 89 wherever I was driving through What would be my best option? Would running one tank really hurt it, well itd be half a tank cause during trips I fill up every half tank. Or should I take the fifteen minutes to retune?
 

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^you'd likely be ok, just would need to listen for detonation/pinging. If your scenario happened to me I'd fill up and listen closely, if it sounded fine I'd continue driving (with an alert ear), if it pinged I'd change the tune. Also, I wouldn't drive it hard (heavy throttle).
 

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I believe there is away to pull back the 91 tune to run with 89 fuel. I am not fully sure on the ratios for that and I know I saw it somewhere on here. Pretty sure it was in the DSP section so dive on in there and see what you can find. That is where I founded all my information on my Trinity before I pulled the trigger on it. Dig in and see what you can come up with and good luck with whichever route you go with. Keep us updated.
 

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I have a question on this. I understand everything stated already, but I travel often and if I were to need to fill up and the best available was 89 wherever I was driving through What would be my best option? Would running one tank really hurt it, well itd be half a tank cause during trips I fill up every half tank. Or should I take the fifteen minutes to retune?
One tank wont hurt it. Youll be fine. Like has been stated, itll pull the timing and you probably wont even notice it. I personally wouldnt do it daily. Where do you travel that only has 89? Is it higher elevations? If thats the case, then it might not even pull timing as the air isnt as dense and higher octane isnt needed.
 
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