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Octane Ratings


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I got into a discussion with a fellow worker today regarding octane rating. He says that 93 octane will make more power than 87. While I agree with that........ the motor has to have to compression to make the difference. On a car with say 8.5/1 compression 93 will make very little difference over 87. On a 11/1 compression the whole thing changes.

 

If you are pulling a heavy load the higher octane will work better and cause less detonation because of the slower burn rate.

 

This is assuming that no knock control exists.

 

 

I also say that the higher the octane rating the slower the burnrate.

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The computer in the truck is optimized for the octane rating listed in the owner's manual.  It' won't run any better with 93 unless you have an aftermarket tune.  To me, it's not worth the $0.20/gallon difference.

 

 

 

 

Yep....I argue with friends about this all the time. They think that burning the mid-grade fuel 88-89 gives them more power in a stocker....... :cheers: Not unless the engine, computer, etc is rated for higher octane will you see any performance increase. You may feel good about it but that's it... :D

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My aunt has a ~1992 Buick LaSabre with a V6. It has been an awesome car for her but when she first got it they had problems every now and then. They eventually took it to the local dealership to resolve the issue. It turned out to be that they were occasionally using 93 octane fuel. The dealership actually had to call the engineering division for the vehicle to figure out the problem. Her particular model was specifically designed to burn 87 octane and using a higher octane caused her vehicle to go ape shi_. I had never heard of this before but I know that it is true.

 

 

Fred

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This is a common misconception, and it's constantly and consistently propogated by the friggin oil companies (to make more money of course). :cheers:

 

Higher octane by itself does not develop more power, it's all in the engine itself. Octane is simply a measure of energy and "resistance" to detonation. The higher the octane, the higher the resistance, therefore needing more compression/timing to get it to burn completely. Higher octane in an engine rated for 87 doesn't burn completely and will cause all sorts of carbon build up over time. That leads to hot spots, detonation, pinging, and all sorts of other maladys.

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OK I guess it's time to post this again:

 

http://www.vettenet.org/octane.html

 

 

 

 

 

I can site here and give 100 reasons why not to run higher octane fuel unless it was recommended by the manufacturer. But I'm not going to waste the time because its not going to change anyones mind one way or the other.

 

So all Im going to say is dont believe everything you read, especially on the internet. I know 13yr olds who could make more proffessional, more believable, an detailed websites on a subject like this.

 

Oh wait! a 2 second yahoo search just disproved everything said

 

http://www.handymanusa.com/articles/octane.html

 

http://www.csgnetwork.com/octaneratecalc.html

 

http://theserviceadvisor.com/octane.htm

 

 

and even "how stuff works"

 

"6.14 Does low octane fuel increase engine wear?

 

Not if you are meeting the octane requirement of the engine. If you are not

meeting the octane requirement, the engine will rapidly suffer major damage

due to knock. You must not use fuels that produce sustained audible knock,

as engine damage will occur. If the octane is just sufficient, the engine

management system will move settings to a less optimal position, and the

only major penalty will be increased costs due to poor fuel economy.

Whenever possible, engines should be operated at the optimum position for

long-term reliability. Engine wear is mainly related to design,

manufacturing, maintenance and lubrication factors. Once the octane and

run-on requirements of the engine are satisfied, increased octane will have

no beneficial effect on the engine. Run-on is the tendency of an engine to

continue running after the ignition has been switched off, and is discussed

in more detail in Section 8.2. The quality of gasoline, and the additive

package used, would be more likely to affect the rate of engine wear, rather

than the octane rating."

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