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Discussion Starter · #1 ·
Hello everyone who is reading this, I have a 2002 Mustang GT with 78k Miles and I wanted to know if I can run 100 octane fuel from Arco or another gas station but the Arco near me has 100 octane, I also currently run on 91 octane with the modes listed below:

78mm BBK Throttle Body with an Airraid MXP Series Cold Air Intake, MSD Coil Packs, with an Off-Road X-Pipe with SLP Loudmouth 1 leading out the back. I also replaced the TPS and the IAC.

I don't have a tune either but I do have the X3 Bama Tuner I bought off a guy on Offerup but no tunes on it. It is unlocked and Ive messed with it on the car a little bit but would I need a tune to run 100 octane? Thank you guys
 

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You have nothing to gain by running 100 octane without a tune IMHO.
 

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Agreed with crjackson -- there is no gain in running 100 octane if the car is not tuned for it. It might actually be worse, could cause carbon build-up over time.

Octane rating has nothing to do with "power content" in the fuel. Octane is simply a measure of resistance to detonation; basically fuel with higher octane burns slower. This higher resistance to detonation allows you to run more timing advance without pinging. The timing advance is what gives the performance boost, and the octane lets you do it.
 

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But then you run in to where the engine makes the best power. You have to know if your engine is going to be octane limited as far how much timing it will take. More timing does not always mean more power, and the engine will make the same power regardless of fuel used. The fuel only helps prevent detonation and allow the engine to reach its full potential ONLY if you are octane limited. Meaning, if your engine makes the best power possible at 28° then it will make the same power at that timing with any fuel. You only need to change fuel if you experience detonation at or before the 28°.
 

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I have to laugh a bit..... this question has been asked for many decades! As an FYI- Engine Masters just did a test on an engine to see if there was any difference in HP/TQ using 86*, 91*, E85, 110 and 116 octane fuel (pump gas....and yes, california)..............

Here i the same (validated) answer that i have said for years................ the HP/TQ will be the same except for the E85 which will produce a bit more hp/TQ because of the extra oxygen molecule..................
 

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Discussion Starter · #6 ·
Is it possibly for new edge mustang engines to run E85? My engine is a built 2006 Grand Marquis Engine that I took apart and rebuilt for my mustang
 

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It is possible as long as your fuel pump and injectors are made for it. E85 is corrosive. You also have to adjust the tune for it and test every tank you run. There are different stoich points for each ethanol level so a tune change is needed if you run e70, then the next tank is e80, you have to change the tune for that. E85 is a pretty big hassle.
 

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Discussion Starter · #8 ·
Okay so I tested it out, threw in 100 octane racing fuel from the Arco gas station and felt a little noticeable difference. I was originally just using 91 octane bout 4 bucks a gallon, so I let the gas tank completely empty and then filled it about a little over a quarter of gas, and drove it around and I have rumbles and pops, they got bigger, my back tires spun, and the pull was a little stronger. Just thing is the gas burnt out faster, and its about 6 bucks a gallon. I just used most of it up and going back to 91 for the time being budget-wise but I think with a tune, it would have significant changes.
 

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perceived increase in performance combined with higher fuel consumption is most likely the result of a heavier throttle foot combined with wishful thinking
 
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