High Octane Fuel
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Intermediate
Joined: Oct 2006
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High Octane Fuel
Is there any benefit to be gained from running fuel with octane greater than 93 in a stock C6? I can get 100 octane and was wondering if it was worth mixing a few gallons of it with 93 octane. Would it harm the engine as long as it is unleaded fuel?
Racer
Joined: Mar 2007
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From: DFW Texas
higher octane fuel is less volatile, meaning it contains less BTU's per gallon. The increase in octane is only there to help the fuel withstand higher compression ratio's without auto-igniting. Meaning, unless you increase your compression ratio by rebuilding your engine with different stroke, crank, pistons... etc..., you're better off using the octane that the car is built for. It won't hurt your car, but you'll get less power from a higher octane fuel.
Le Mans Master
Joined: Aug 2001
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From: Bradenton FLORIDA
higher octane fuel is less volatile, meaning it contains less BTU's per gallon. The increase in octane is only there to help the fuel withstand higher compression ratio's without auto-igniting. Meaning, unless you increase your compression ratio by rebuilding your engine with different stroke, crank, pistons... etc..., you're better off using the octane that the car is built for. It won't hurt your car, but you'll get less power from a higher octane fuel.
Exactly! We are a VP racing fuels dealer and we have to educate people on this all the time. 
Instructor
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From: Escondido Ca
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Instructor
Joined: Dec 2005
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From: Escondido Ca
Well, I do not know if fuel works like this or not but. If I mix 12 gal of 91 to 4 gal of 100 I would get an average of 93.25. So unless there is something spacific about fuel octane the 5 gall per tank should yield approx 93 octane.
CF Senior Member
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From: Tucson Arizona
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Melting Slicks
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From: Houston 06 C6 Ysi SC 402 fgd TX
Makes me wonder
That's what I had thought intuitively. That our cars are designed for a specific octane rating. So the octane booster, octanium that is "the rage" and others that boosts octane to 100, it really is not designed for our engines? So somebody chime in gimmik or no?
I have yet to see a dyno sheet comparrison HP and torque curve with 93 vs 100. I wonder why?
I suppose if you are either drag racing, or autox, all day in 105 degree temps as the car pulls timing the 100 octane could reduce the pulled timing? and or prevent if from detonating or knocking?
On another note, you could have a around town tune for regular 93. and then on race day, put your 100 octane tune in as it could give you a few more ponies?
I have yet to see a dyno sheet comparrison HP and torque curve with 93 vs 100. I wonder why?
I suppose if you are either drag racing, or autox, all day in 105 degree temps as the car pulls timing the 100 octane could reduce the pulled timing? and or prevent if from detonating or knocking?
On another note, you could have a around town tune for regular 93. and then on race day, put your 100 octane tune in as it could give you a few more ponies?
Pro
Joined: May 2006
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From: Los Angeles CA
I think I remember reading on here that if you put in higher octane the ECU can adjust timing for slightly more power. I have no idea if this is true or not though, perhaps somebody else can elaborate?
Advanced
Joined: Apr 2007
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From: Venice Florida
89 to 93 octane
I was reading in Popular Mechanics that 89 to 93 makes no difference as long as you don't change it up. Basically keep one grade and stay with it so the car doesn't have to adjust back and forth. They also said that 93 octane will only make a difference in very high performance cars and motorcycles (F1, Sport bikes, etc.) very high RPM. They said it will not harm your car or reduce performance in any way using the lower grade which is usually 89.
Drifting
Joined: Jul 2005
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From: az
I was reading in Popular Mechanics that 89 to 93 makes no difference as long as you don't change it up. Basically keep one grade and stay with it so the car doesn't have to adjust back and forth. They also said that 93 octane will only make a difference in very high performance cars and motorcycles (F1, Sport bikes, etc.) very high RPM. They said it will not harm your car or reduce performance in any way using the lower grade which is usually 89.
they are clueless when it comes to our cars. datalogging from a local forum member shows constant part throttle (like 35%tp) KR even in 1st gear with 91 octane gas (which is highest you can get here) in iat above 90*. i had owe honda cbr sport bikes the last 9 years and all the manuals call for 86 octane, so they are clueless too on sportbikes.
Advanced
Joined: Apr 2007
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From: Venice Florida
they are clueless when it comes to our cars. datalogging from a local forum member shows constant part throttle (like 35%tp) KR even in 1st gear with 91 octane gas (which is highest you can get here) in iat above 90*. i had owe honda cbr sport bikes the last 9 years and all the manuals call for 86 octane, so they are clueless too on sportbikes.
Even on my Infiniti it says put premium only.
Race Director
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The high octane tables are setup for 93 octane, the low tables are set for 87. It switches back and forth between the high and low octane tables based on knock count. Other things can modify spark advance too. It looks at IAT, coolant temperature, etc and makes changes depending on particular conditions. But in general all of those changes are downwards, not upwards. So the 93 octane tables are as high as it goes, unless you have a tune done that raises those values.
Drifting
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From: az
Advanced
Joined: Apr 2007
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From: Venice Florida
Advanced
Joined: Apr 2007
Posts: 65
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From: Venice Florida
I also find it funny with the 600cc bikes using mid grade stuff when it's a higher revving engine. Not sure about compression though.
Edit: You are right with the 6's, I read a few clips that say use 86 or higher in that manual and it's designed to use 87.
Edit: You are right with the 6's, I read a few clips that say use 86 or higher in that manual and it's designed to use 87.
Last edited by Irish C6; May 17, 2007 at 03:33 PM.
Instructor
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From: Saginaw Michigan
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