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Just curious if everyone is following the recommended octane stated in the manual. Post here what you are running in your car.
I do follow what is specified in the manual.

Bob
 

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RobertR said:
Just curious if everyone is following the recommended octane stated in the manual. Post here what you are running in your car.
I do follow what is specified in the manual.Bob
I'm a great believer in following what the mfgr states; so yes, I use 89 octane exclusively.
 

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On page 250 of the manual, it states premium is not recommended for the 3.5 and 5.7 liter engines. My dealer told me it would damage the engine if I used premium.
 

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PR300C said:
No 89 octane available here. Only 87 or 93, si I'm using 93 octane.
Wouldn't know if there's a difference .....
Were do you live? That's odd that they don't have 89.
 

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I have been running 93 octane only.

I'll have to look into the book and read about it "damaging" the engine... Never heard of that before.
 

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Fast4Door said:
I have been running 93 octane only.

I'll have to look into the book and read about it "damaging" the engine... Never heard of that before.
The Owner's Manual is rather clear about NOT using 93 octane.
 

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Robert E Thompson said:
I use 91 octane is this ok
PLEASE read the owner's manual. It is very specific about NOT using higher than 89 octane. And they don't particularly want you to use anything else. Don't remember the page but go to the index and look under "octane". Couldn't be easier.
 

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Yes... higher octane can damage you engine. Higher octane burns hotter/ more intense burn in the combustion chamber. The only times you need higher octane fuel is 1.the engine knocks or pings 2.the manufacturar say's too 3.racing or you just want too pay too much money for gas.
 

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True.....

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 don't know what I think about any of this. It's OK to go from 89 to 87, but with a bit loss in power. It's not OK to go from 89 to 91 or 93 because it will damage the engine? Regardless, I buy gas in KC at Cosco which offers 2 grades 87 and 91. Price is best in town for both grades (at least on the Missouri side, Kansas has more taxes). So when the 300C finally comes in, I will be putting 91 octane in. I trust that any timing changes that the computer makes to adjust for 89-->87 octane, will also adapt to an 89--->91 octane gas.

Most cars/trucks I have had all seem to run a bit smoother on slightly higher octane gas. Less knock sensor interferance. Just my $.02 :)
 

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87 octane

So far I have run only 87 octane. I've always learned that an engine will ping if the octane is too low, letting you know damage could occur. I have never heard pinging of any sort.

That being said, my gas mileage has been a bit low (16-17 70% city, 30% hwy). If I knew for sure that 89 octane would improve my gas mileage, I would certainly switch.
 

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You won't hear pinging on modern engines. Long before you would notice it any pinging is picked up by the 2 knock sensors mounted in the engine block. The computer will then retard timing until the pinging is gone. All automatic. The result of course is no engine-damaging pinging, but there is also a decrease in performance because of the retarded timing. On proper fuel the computer will allow full advance (and best performance).
 
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