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Discussion Starter #1
Just wondered what everyone is using in their 5.7 Hemi for Octane Grad? The manual says 91 or higher. Any pro's or con's for using 93 octane? Besides the price!
 

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If your manual says 91, that is what I would use. If you move up to 93 octane gas, it's a waste of money if your car isn't tuned for it.
 

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The octane grade that I run in the RT is 91. There are the options of cheaper fuels with lower octane levels but, the price one may save at the pump could come at the price of your engine. Therefore, it is best to use what's recommended for the engine itself. Low compression engines can get by with 87 or so. Higher compression ratio's require more stable fuel and thus greater octane. Otherwise you get pinging, knocking, dieseling and the dreaded hole in the piston.
 

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Just wondered what everyone is using in their 5.7 Hemi for Octane Grad? The manual says 91 or higher. Any pro's or con's for using 93 octane? Besides the price!
You only need 91 octane if you have a manual transmission.

If you have an automatic transmission, then the manuals for my previous 5.7's (2011 Challenger R/T Classic and 2013 Charger R/T Plus) and my current 2017 Durango R/T all called for 89 recommended --- which is what I used --- with 87 being acceptable.
 

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The Wizard is correct! 91 only needed with the manual, 89 recommended with the auto.

Keep in mind you get no benefit of using higher octane than what the engine was designed for, the oil companies LOVE you though!
 

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I have a similar question. I currently run 91 octane fuel in my 13 SRT8. I just orederd a Diablo T2 so will be tuning it in the next few weeks.

However here in town there are 2 gas stations called JumpStart that has 93 octane that has 15% ethanol and is about 20¢ cheaper than 87 octane so thats about 40 to 50¢ cheaper than 91 octane. Thats a price I have to take into consideration. The manual says 10% ethonal max but a 50/50 mix could save money and average higher octane. Any thoughts on this?
 

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Discussion Starter #7 (Edited)
1. I have a 5.7 Hemi with a 6 speed. My only options at the pump is 89 octane mid grade or 93 octane premium. Should i go with 93 octane?
2. How do I get it tuned for 93 octane?
3. Why does a 6 speed require a higher octane than an automatic??
 

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The 91 minimum is stated as in different regions you have varying gasoline blends.

In many states that require reformulated gasoline (CA, high altitudes, high smog zone areas) the highest octane rating is typically 91

When I lived in the PNW the octane ratings for premium were typically 92

Here in NC its 87 / 89 / 93. Frequently you can find non-ethanol fuel in either 87 or 90.

Running 93 in your M6 R/T is fine - for the warmer weather, that little extra will help keep spark knock reduced and give you a little more low end and keep the mpg up vs. what lower grades of gas would do.
 

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3. Why does a 6 speed require a higher octane than an automatic??
Some say it's tuned differently and some say it's a hedge against detonation for people who don't know how to drive a manual and will lug the engine.

Power difference is only 3 hp and the 2.5 inch exhaust and bottle mufflers could explain that.

Would have to see a log of the tunes side by side to know.

Sent from my SM-N920T using Tapatalk
 

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acer- what model year is your car? My 2012 R/T calls for mid grade 89 octane. I usually do 89, then a half or quarter tank of premium. I'm always combining gas.

All gas in Illinois has ethanol as politically it's a big corn growing state. My biker friend swears that if you use gas that contains 10% ethanol, then you lose 10% horsepower, and your 375 hp R/T is now minus 37.5 hp, for a 337.5 hp engine. I don't know if that's true, but I know ethanol is not good for large equipment engines such as tractors and excavators.

Luckily I can find NO ethanol premium in neighboring states, so I put that in my tank every couple of weeks. Maybe the best thing you can do is put NO ethanol gas in your R/T if you are concerned about fuel quality, if you can find it.
 

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Hmmmmmm....my manual for my SRT 392 says 91 or higher....not 87 or 89.
The question was about the 5.7, try to pay attention would 'ya?? :grin2:
 

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For your consideration-

How do you know it’s actually 91 coming out of the tank?

As gas sits, it degrades. Buying from a premium vendor that fills regularly can help, but how long did it take to actually truck it and get it there?

By the way, how much ethanol is actually mixed in? How much water did it absorb in getting to your tank?

How much stuff is sitting in your heads and combustion chamber right now?
How hard are you running the car?
How long are you going between fill-ups?

So, if the manufacturer of both the car and the gas set a margin of safety to cover all this, no worries.
It’s likely you can fill on 91 all day with no issues.
For me, I hedge against issues, and fill with the highest grade I can find at a given pump, and always try and keep it to 91 or better.

With the blower going on, it’s water/meth specifically because I don’t trust the gas in Alaska, as testing tends to report 1-3 points lower actual octane than advertised for sale. So, BOOSTane is getting a phone call, and I have the w/m.

For a plain-jane 5.7, I don’t suspect you will ever have an issue with 91 if you live in a place that doesn’t suck, and you have some assurance of a reasonable level of consistent quality.

I just wouldn’t race on it, nor subject the car to maximum demand performance-wise. Not the way you want to find out your gas is a point or two down on octane below what you purchased.

Cheers,

Chuck
 

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I don't have enough money to pay attention ever since I bought this damn SRT!
"What's ole Crazy Pete been up to lately?"

"I heard he bought himself a fancy Dodge Charger and now he's broke."

"Broke? Crazy Pete?? Really?!? Just how broke are we talking here..."

"So broke, he can't even pay attention now!!"


... That exchange, or one very similar to it, is being overheard more frequently in local diners and area coffee shops all around Buffalo, NY lately... :wink3:
 

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I run 89 in mine, which is what the manual calls for, like others have said with 87 being acceptable. I did run 2 consecutive tank fulls of 108 race gas, If I remember correctly, I paid about 8.00 a gallon. it did absolutely NOTHING to improve performance, well that's a lie, it shed some weight from my pockets so I might have picked up 0.0001 0-60 time. :D
 

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"What's ole Crazy Pete been up to lately?"

"I heard he bought himself a fancy Dodge Charger and now he's broke."

"Broke? Crazy Pete?? Really?!? Just how broke are we talking here..."

"So broke, he can't even pay attention now!!"


... That exchange, or one very similar to it, is being overheard more frequently in local diners and area coffee shops all around Buffalo, NY lately... :wink3:
Lol....except I have a Challenger. Stupid Buffalo people. They cannot even gossip right!
 

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I have a similar question. I currently run 91 octane fuel in my 13 SRT8. I just orederd a Diablo T2 so will be tuning it in the next few weeks.

However here in town there are 2 gas stations called JumpStart that has 93 octane that has 15% ethanol and is about 20¢ cheaper than 87 octane so thats about 40 to 50¢ cheaper than 91 octane. Thats a price I have to take into consideration. The manual says 10% ethonal max but a 50/50 mix could save money and average higher octane. Any thoughts on this?
The maker of the tune should offer some guidance regarding what grade of octane should be used. You should avoid applying a tune that requires an octane grade of gasoline that is not readily available to you.

As for 15% ethanol, my digital copy of the 2018 Challenger owners manual has this to say about the 6.2l engine:

FUEL REQUIREMENTS

6.2L Supercharged Engine

Do not use E-85 flex fuel or ethanol blends greater than 15% in this engine. These engines are designed to meet all emissions regulations, provide optimal fuel economy and performance when using high-quality unleaded “Premium” gasoline having a posted octane number of 91 as specified by the (R+M)/2 method. The use of 91 or higher octane “Premium” gasoline is required in these engines.

Looks like up to 15% ethanol is fine. Chances are the amount of ethanol will be less than 15%. With "10%" ethanol my info is refiners erred on the side of caution and the actual percentage of ethanol is in the 7% to 8% range. But even if you get 15% ethanol the manual says that's ok. Just nothing above that.

'course, the engine will be the final judge. While I haven't come across this in the Dodge manual with other cars regarding gasoline there was something to the effect if the engine reacted poorly to a brand of gasoline to try another brand. Engines vary in what they like and gasoline can vary from region to region.

Be sure whatever gasoline you try and decide to stick with you buy it from a busy station to avoid the chances of stale gasoline.
 

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Lol....except I have a Challenger. Stupid Buffalo people. They cannot even gossip right!
Whatever the defect in a person's brain is that will not allow them to recognize a Challenger is NOT a Charger cannot be limited to any one region like that. I see it on the news around here, and I hear it from people I work with, live next to, and talk to on the phone who live thousands of miles away ("You still got that Charger? I still have my Challenger, yes. Charger, Challenger, whatever, they look the same!"). I even have family members who know me quite well, well enough to know I am nothing if not passionate about my Challenger(s), and yet they will still call it a Charger most of the time when asking about it.

No, whatever it is, I'm afraid it's nearly universal at this point. It has spread all over, and there is no stopping it from spreading further I suspect. The best we can do is just correct them when we have the energy to and ignore them when we don't.
 

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Whatever the defect in a person's brain is that will not allow them to recognize a Challenger is NOT a Charger cannot be limited to any one region like that. I see it on the news around here, and I hear it from people I work with, live next to, and talk to on the phone who live thousands of miles away ("You still got that Charger? I still have my Challenger, yes. Charger, Challenger, whatever, they look the same!"). I even have family members who know me quite well, well enough to know I am nothing if not passionate about my Challenger(s), and yet they will still call it a Charger most of the time when asking about it.

No, whatever it is, I'm afraid it's nearly universal at this point. It has spread all over, and there is no stopping it from spreading further I suspect. The best we can do is just correct them when we have the energy to and ignore them when we don't.
I pulled my CHALLENGER into the service department in-processing bay at my DODGE DEALERSHIP yesterday. There to be inspected for the extent of some rodent damage to some wiring. The service tech at the DODGE DEALERSHIP, sitting there, looking through the huge glass window into the service bay, looking at my shiny black CHALLENGER with the R/T stripes, and the word "Challenger" on the fender, while filling out the work order asks, "This is a Charger, right?". I almost got in and drove it across the street to the Chevy dealer to see if they knew what kind of car I had.
 
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