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Discussion Starter · #1 ·
I'm getting wuite some confilicting info on the fule octane requirement on the Hemi. The Chrysler website during the "compare vehicles" session on the 300C shows "unleaded'. ONe of the magazine tests like Road & Track or MotorTrend said 89 (unleaded plus). I asked Chrysler marketing and the "simple" answer was "Premium". Can any of you users please advise what is working in your vehicle?
Also, for the "techies" on the forum - Kansas gas stations have a lot of Unleaded Plus that 89 octane is obtained by ethanol alcohol. Any input is certainly appreciated.
I am placing my final commitment on a 300C that someone else "bailed" on. I will still keep it if Premium (that's what I thought it would be when the "interest" in Hemis forst formed in my mind). I'd just like to know.
Thanks in advance!
 

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You might find this thread helpful.....

http://www.300cforums.com/showthread.php?t=318


Here was my 2 cents...... Keeping in mind the recommend octane fuel for the 2005 Hemi is 89.... 87 is ok.



Octane = Residence to burn

The higher the octane the longer the molecule chain. Which in turn means to things.

1) It's harder to burn (takes more heat to combust)

2) you will get more "power" out of it, because there is more of a molecule to break down.

So, an engine is designed to run at a certain temp and compression ratio. This translates to what octane level fuel you should use.

In a high performance engine "high temp and high compression ratio" you need a fuel that will only ignite when the spark goes off. Not ignite because of high temp before the spark. (Thats why you get poor performance when you use 87 octane in an engine that was designed for 92, the fuel keep burning before the spark)

Now, the other way..... The fuel could "potentially" burn after the spark or take to long because the temp and compression was to low. But, I think this is less likely that the other way around.

So, unless you have a problem ... I think you should use the octane that was designed for the engine.

My 2 cents
 

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I agree to a certain extent that you should use the fuel specified by the manufacturer and that appears to be 89 Octane. In Australia we have Shell pushing their Optimax 98 RON (Octane) high density fuel with claims that you get better mileage. My 3.8 Litre supercharged V6 (Buick engine) is specified for "premium" (95 RON) and I can report it does definitely perform and get better mileage on 98 RON.

The best advice then is don't use less than recommended and try the dearer fuel to check yourself if to makes any difference in both power and economy.
 

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My manual specifically states for the 3.5L and 5.7L engines:

"The manufacturer recommends the use of 89 octane for optimum performance. The use of premium gasoline is NOT recommend."

I only use 89 octane in my HEMI as that statement in the book is pretty concise and to the point. Why screw with it.
 

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badness said:
My manual specifically states for the 3.5L and 5.7L engines:

"The manufacturer recommends the use of 89 octane for optimum performance. The use of premium gasoline is NOT recommend."

I only use 89 octane in my HEMI as that statement in the book is pretty concise and to the point. Why screw with it.
This is exactly correct, Follow the book, the dealer who said "premium" is an idiot. In a previous thread on this topic someone mentioned that premium would damage the engine.
 

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Discussion Starter · #7 ·
Thanks for all your replies. Actually I sent an e-mail to Chrysler direct while the dealership was closed - and why take a chance the dealer would get it wrong - right? Well, the answer came in from Chrysler itself. She was a "Senior Staff Representative -
Chrysler Information Center". Then I reread one of the tests in one of the auto mags and they stated 89 Octane. Thanks for the "heads up". I ordered a copy of the owners manual yesterday so I can read up while I wait for the car to be made. It's just too nice of a car to screw up using the wrong fuel. Thanks for everyone's input!!!!
 
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