View Poll Results: What fuel grade
87
1
1.52%
89
1
1.52%
92
64
96.97%
whatever's cheap
0
0%
Voters: 66. You may not vote on this poll
What kind milk do you give to your baby?
03-25-10, 03:29 PM
#29
I use whatever's highest, usually 94. I've also noticed my car seems to run better on certain gas stations? Seems my car likes Shell the best. You guys notice anything like that?
Also, I've always wanted to try 100 Octane, or race fuel. But I was told that was a bad idea on a stock engine. It would harm it if anything because higher Octane's are too dry or something? Is this true?
Also, I've always wanted to try 100 Octane, or race fuel. But I was told that was a bad idea on a stock engine. It would harm it if anything because higher Octane's are too dry or something? Is this true?
03-25-10, 05:34 PM
#30
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Octane has nothing to do with quality. 87 octane is just as good of quality as 91 octane. The difference is in resistance to detonation. During the compression stage in a 4 stroke motor the mass of the air/fuel mixture stays the same while the volume is decreased therefore the temperature of the mixture rises according to Boyl's law. If the air/fuel mixture reaches the heat of combustion prior to the spark plug igniting, the mixture will detonate (hence detonation).
87 octane is typically safe on engines up to around 9:1 compression. 91 is the minimum recommendation for motors over 10:1 compression as the A/F mixture will become hotter on a 10:1 motor during the compression cycle vs a 9:1 motor. 91 octane has a higher heat of combustion than 87. This is not to say your motor will definitely detonate with 87, but under the right conditions it could. 91 it's far less likely.
Cliffs- use 91 octane on our motors that range from 10:1-10:5 compression depending on year
87 octane is typically safe on engines up to around 9:1 compression. 91 is the minimum recommendation for motors over 10:1 compression as the A/F mixture will become hotter on a 10:1 motor during the compression cycle vs a 9:1 motor. 91 octane has a higher heat of combustion than 87. This is not to say your motor will definitely detonate with 87, but under the right conditions it could. 91 it's far less likely.
Cliffs- use 91 octane on our motors that range from 10:1-10:5 compression depending on year
Where octane is raised by blending in ethanol, energy content per volume is reduced.
Given that and the previous information I would assume and have been told before that you would want to use the lowest possible octane that does not cause pre-detonation in your engine to achieve maximum power and the best fuel economy.
I usually run a mid grade because I do alot of hwy driving for work and spend a ton of money on fuel. In the winter when the air is more dense and the engine more prone to pre-detonation I use premium.
Also the higher the octane you run the quicker you will foul out your spark plugs.
Last edited by MAJones; 03-25-10 at 05:37 PM.