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Discussion Starter #1
The only thing I have ever used in my SRT8 is 93 oct when it was Stock or with the blower. Now, the R/T has more compression than my SRT8 does so I figure it will be best to use 93. The VVT does make a differance so the 93 thing could be wrong on my part. Has anybody noticed a differance in performance using 93 over 89 in the R/T's???
 

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ive had my R/T for about 2 months now and has 4900miles on it and i have always used 89 and it runs fine. one time i did use 93 and didnt notice a difference.
 

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With the price of gas.....I run 87. I do mostly highway driving. Now when racing, I put in the predator 93 tune, and run 93, but afterwards, it goes back to the 87. It is within the recommendations.
 

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My '10 I initially ran 89 but was getting a mysterious misfire in #5 cylinder When i got on it hard. Went to dealer several times, no answers. I switched to 93 and have not had the misfire since. I don't know if that was the issue or not, but I'm sticking with 93.
 

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I've got 32K miles on my RT. I typically run 87 octane. In the heat of the summer I notice a little detination. 89 eliminates it. There is no reason to run 93 octane in an RT. I do put some in to mix it with my 87 octane sometimes in the summer to bump the numbers up and eliminate the detination. I do have an automatic.
 

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93 Octane I put in my RT 6spd most of the time if not 92 or 91. 35,800 miles
 

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I saw/read it somewhere that 91 or better for the 6 spd R/T and 87-89 for the auto, but I cant remember where I saw/read it. I've been running 93 in my 6 spd. But run what doesnt ping/detonate.
 

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Discussion Starter #10
Im gonna put my Aeroforce gauge from my Charger into the R/T for a day or 2 to see if I get any knock on 89. I have to run out this 93 first.
 

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93 all the time for me ..... my Rt loves it ....
 

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93 OCT. These motors are 10.5:1 - that needs premium.
 

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I use 93 myself. The six speeds requires 91 or higher according to my owners manual. Autos need a octane rating of 87 to 89.
 

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Ton of misconceptions in this thread regarding octane. First and foremost, the higher octane fuel means that it has a higher flash point. It burns slower than a lower octane fuel.

If you car does not require anything more than 87 octane, there is no reason to run anything higher. For example, if your R/T only requires 89 for optimal performance with the factory tune, running 91 or 93 will only result in an incomplete burn resulting in deposit build-up on valves, unspent fuel resulting in less MPG, decrease in performance, etc...

Run the lowest octane possible to achieve the best performance. :thumbsup:
The SRT 6.1 requires higher octane with lower compression than the R/T because of a thing called dynamic compression. The VVT in the 5.7 allows for a higher statically rated compression, lower dynamic compression vs. the SRT 6.1.

6.1 technology is old compared to the VVT of the 5.7. Glad to see Dodge moving to something better in the next SRT. :)

Hope this helps.
 

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I have my R/T since February 09. I did not notice any difference between 89 or 93. I have over 11,000 miles on it. Most of the time I use 89 but a few times when on a trip they had 87 or the 93. No difference felt between them.
 

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Word for word from the 09 owners manual page 317-

5.7L Engine (with Manual Transmission)
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.

Word for word from the 09 owners page 316-

3.5L and 5.7L Engines (with Automatic
Transmission)
The 3.5L and 5.7L engines (with automatic
transmission) are designed to meet all
emissions regulations and provide satisfactory
fuel economy and performance when
using high-quality unleaded gasoline having
an octane range of 87 to 89. The manufacturer
recommends the use of 89 octane for optimum
performance. The use of premium gasoline is not recommended,
as it will not provide any benefit over regular
gasoline in these engines

Listen to your owners manual. You'll get all kinds of incorrect info on the internet, but the owners manual will be right. And if a warranty issue ever arises, the info you followed in the manual will back you up.
 

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Even if you run 89 in a Manual R/T or SRT-8 it will just force the PCM to adjust fuel/Spark tables and retard ignition timing. You might lose 4hp at the most. You will not damage your car running 89 in these motors. In fact many parts of the country (New Mexico) do not have many places where you can even get 91.
 

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I use 93 myself. The six speeds recommend 91 or higher according to my owners manual. Autos recommend a octane rating of 87 to 89.
Corrected the statement
 

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