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So I know that the manual and alot of people in this board go with and reccomend 89octane in the 5.7, and frankly I like to run it too.

I recently got a Costco card, and was looking forward to cheap fuel for the Hemi, at 15 cents per litre cheaper than the other gas stations.

I pull up to the pump, and there is 2 buttons. 87.... and 91.

I said "oh what the %#^"

So I chose 87, cause its acceptable and its what the previous owner and alot of other people run in it.

So the question is.

Should I, and can I run the 91 octane safely to get the benefits of the higher octane? Or should I continue on with 87. With the fuel savings even at 91 octane, I can choose to run either.

Will it have to advance the timing so much it wont run right with 91?

Opinions? Wisdom? Help! :)

Thanks as always!
 

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Nut up or Shut up
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I have used as low as 85 octane in my Hemi with no noticeable negative side effects. I thought the manual recommended 87. I dont think you will have any problems running 87. I use 87 right now and it does just fine.
 

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Shut up and drive!
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running the 91 will be just like running the 87. A little bit of performance loss. Many people think running 91 in something designed for 87 or 89 will make it better, but the difference between octanes is the speed that it burns. 87 burns quicker then 91. by the time your truck fires and burns without any timing adjustments, its a waste of power.

Ive been to a few stations here in WA that did not have 89(back when I was on my stock tune) and i ended up putting about 60% 87 and 40% 91.

You wont notice anything major with 91, but without tuning, its not going to do anything more for you
 

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Im wired!!!
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93 octane on a stock tune the truck runs like shit. i never had a problem with 87, the truck liked that the best on a stock tune.
 

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When I go to Costco (or Sam's), I just mix the gas. Roughly 70% 87 and 30% 93. I figure that's getting me close to 90 or so. We do that for both Hemis if we're filling up at either of those places.
 

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