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What octane do you use??

  • 87

    Votes: 11 7.0%
  • 89

    Votes: 57 36.1%
  • 91

    Votes: 35 22.2%
  • 92

    Votes: 8 5.1%
  • Higher than 92

    Votes: 47 29.7%

  • Total voters
    158
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Discussion Starter #1
Just curious as to what the norm was around here????
 

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I used 89 octane untill now and I got a predator and I'm putting 93 in it so I can put a tune in it. 0% ethenol
 

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These engines are well known and reliable, I follow the recommended octane as prescribed in the owners manual
 

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Regardless of an engine being "reliable" it's nice to run 93 every month or so if you run 87-89 most of the time, cleans it up.
 

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Sunoco 91 Octane with a Predator custom tune.
 

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I plan to keep using 87 oct until my ScanGauge readout starts indicating % lean fuel mix hitting below 0% (suggesting rich fuel mix). I anticipate I won't need this until the warm weather hits. For now, that Union 76 regular grade fuel seems to be hangin' in there with a bit of headroom (typically between 3-8% lean, depending on operating conditions).
 

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Regardless of an engine being "reliable" it's nice to run 93 every month or so if you run 87-89 most of the time, cleans it up.
Running the recommended 89 octane does not dirty the engine, and running a higher octane does not clean it up.
 

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Octane is a combustion retardant to keep the fuel charge from pre-detonating.

If you run too little octane (87 in 5.7 Hemi), your fuel could pre-ignite (before sparkplug fires) which causes double ignition, aka 'pinging'.
If you run too much (93 in a lower compression engine), you lose some power, and waste money.

Some advanced high compression engines like the Ford 5.0 Coyote 'self adjust' to whatever octane is encountered. I assume this means lowering the compression ratio somehow or adjusting the timing to reduce the chance of pre-ignition (?/idk) Either way, there will be less power produced, but no damage done. My LS3 is a bit 'dumber' and requires a fuse pull to re-adjust the computer back to high octane if you occasionally put in low octane (which I never would do).

No 'cleaning' ability in octane.
 

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I think most engines since the early 2000's have had the ability to "self adjust" to whatever fuel octane ends up in the tank.
 

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I don't think there is any default "cleaning power" in an Octane rating, but some of the higher octane fuels seem to come with (or at least advertise) various fancy additives to help keep the engine clean while most lower octane variants don't. Maybe its just clever advertising though, to get people who don't need 93 octane to buy it.

Speaking of this, do you guys run any particular "fuel line cleaners" periodically to keep the beast running smooth and clean?
 

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I think most engines since the early 2000's have had the ability to "self adjust" to whatever fuel octane ends up in the tank.
Cars since the 80/90's have had knock sensors which retard the timing if they sense anything amiss with the wrong octane.

If it calls for 87, use 87. ESPECIALLY in this cold weather, anything higher is really just tossing your money out the window unless it calls for premium to be used. You could even run 87 in the 6.1/6.4 but itll just retard the timing and you'll feel a noticeable power loss.

The beauty of the original Hemis was that you could get race engine type power, while using pump gas (and not race gas) because of the combustion chamber hemispherical design.
 

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Nice sig, randy. I spent a few vacations in the UK, and based on my 75 hp rental cars, I realized you don't really NEED more than that for basic transportation. But man, it sure is nice to have 5 times more horsepower than you *need*.

My mom always says "why do you need all that power". I have no good answer, other than when I press the gas and feel the SOTP dyno and hear the roar of the exhaust, I know that I *need* it. Once I took my first test drive, I was sold. No more 4 cylinders for me.
 

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Nice sig, randy. I spent a few vacations in the UK, and based on my 75 hp rental cars, I realized you don't really NEED more than that for basic transportation. But man, it sure is nice to have 5 times more horsepower than you *need*.

My mom always says "why do you need all that power". I have no good answer, other than when I press the gas and feel the SOTP dyno and hear the roar of the exhaust, I know that I *need* it. Once I took my first test drive, I was sold. No more 4 cylinders for me.
Just answer it's A GUY THING!
 

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I don't think there is any default "cleaning power" in an Octane rating, but some of the higher octane fuels seem to come with (or at least advertise) various fancy additives to help keep the engine clean while most lower octane variants don't. Maybe its just clever advertising though, to get people who don't need 93 octane to buy it.

Speaking of this, do you guys run any particular "fuel line cleaners" periodically to keep the beast running smooth and clean?
I think the whole "cleaning power of octane" (mis)conception gets a lot of self-reinforcement when you see sooty accumulation on your exhaust tips after running a tank of regular. It's not because that gas burns dirty, but rather the engine had to run it a little rich because it needed more octane than what it was fed. So the black carbon is just a natural side-effect of the fuel mixture, not its cleanliness.

Now if the conditions are right, such that it does not need to run rich on regular octane fuel, then you won't see the soot (or much of it), either. That said, there are a lot of reasons that will trigger a modern performance engine to adjust to a rich mixture on regular octane. So that opens the door to "reading the conditions" to know when using regular will be just fine, or you can just pump the higher octane stuff and not worry about. It all depends on how anal you want to get about it. ;)
 

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THE RECOMMENDED OCTANE FOR THE 5.7l AUTOMATIC IS 87/89 WHEN YOU MOVE TO THE 6 SPEED 89/91 ONCE YOU START DOING MODIFICATIONS AND CUSTOM TUNING DEPENDING ON WHERE YOU LIVE 93

THIS IS MY SECOND CHALLENGER 1ST ONE WAS A R/T AUTO i RAN 87 AND IT WAS A SLUG BUT RUNNING 89 IT PERFORMED BETTER AND RAN SMOOTHER.

MY 2ND THE 6 SPEED RAN IT ON 89 FOR THE BREAK-IN. WHEN I ADDED THE HEADERS AND CUSTOM TUNE I WAS TOLD TO ALWAYS RUN 93 FROM HERE ON OUT THAT'S ALL I RAN.
 

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Nice sig, randy. I spent a few vacations in the UK, and based on my 75 hp rental cars, I realized you don't really NEED more than that for basic transportation. But man, it sure is nice to have 5 times more horsepower than you *need*.

My mom always says "why do you need all that power". I have no good answer, other than when I press the gas and feel the SOTP dyno and hear the roar of the exhaust, I know that I *need* it. Once I took my first test drive, I was sold. No more 4 cylinders for me.
Thanks for the props! That's the real subtle point to it, as far as regular driving (not racing), that I feel goes untouched, when it comes to these hardy v8's. The pk hp is certainly nice, but in reality, we are just using 150-200 hp most of the time. It's how soon and how easily we can get into that zone that makes these engines such a pleasure. We can dip into this "nonchalantly" w/o even cracking 3000 rpm. That is decidedly more accessible than just having an engine that has only 150-200 hp where you have to rev to a whopping 6000 rpm to get that same power. In a sense, we needed the 370 hp rating, so that we could get the effortless 150-200 hp output. ;)
 

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I run Citgo 93 in my car. 91 doesnt exist here, and 89 isnt enough for my liking.
 

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I have been wondering this myself. Where I am from we only have 87, 89, or 91 octane ratings. I have been using 91 with ok results and fairly good mpg ratings. I recently tried running 87 octane and did not push the car hard and was able to get a really good mpg. So I may look to moving to 89 as a happy medium! I do not race, or have any mods, bone stock 5.7 with a 6 speed!
 

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We have the Hemi in our Jeep with fuel shut off, and the owner's manual states the engine is designed to run on 87-89 octane fuel. They recommend 89 octane for "optimum performance." They also state that using higher than 89 is not recommended as it will not increase performance or mileage. I was running 89, and we recently tried 87 in it. I do not notice a big difference. With the way my wife drives, 87 will do just fine. The reason we switched was we discovered Costco has gas by our house 15 cents cheaper than everywhere else, but they only have 87 and 93. Hey, when you average 14-16mpg, you have to save somewhere!
 

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THE RECOMMENDED OCTANE FOR THE 5.7l AUTOMATIC IS 87/89 WHEN YOU MOVE TO THE 6 SPEED 89/91 ONCE YOU START DOING MODIFICATIONS AND CUSTOM TUNING DEPENDING ON WHERE YOU LIVE 93

THIS IS MY SECOND CHALLENGER 1ST ONE WAS A R/T AUTO i RAN 87 AND IT WAS A SLUG BUT RUNNING 89 IT PERFORMED BETTER AND RAN SMOOTHER.

MY 2ND THE 6 SPEED RAN IT ON 89 FOR THE BREAK-IN. WHEN I ADDED THE HEADERS AND CUSTOM TUNE I WAS TOLD TO ALWAYS RUN 93 FROM HERE ON OUT THAT'S ALL I RAN.
Straight out of the manual:

The 5.7L engine (with manual transmission)
is designed to meet all emissions
regulations and provide excellent fuel
economy and performance when using
high-quality premium unleaded gasoline​
with an octane rating of 91 or higher.

No mention of 89-91 although I'm sure the engine adjusts to whatever you put in it.

Auto does run on regular OK.

Like another post, 91 is not in my area, so I run 93. I guess if I wanted to save a buck or so per fillup I could put half 89 and half 93. I don't have the patience for that.
 
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