E15 gas?
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Your owner's manual, on page 9-51 gives the fuel requirements and it states you can use up to E15 in the car.
Burning Brakes
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From: MN
My FI DI engines really like the higher ethanol blends, supposedly something to do with the additional fuel helping to cool down the combustion chamber. I wonder if that's the case with the LT1's too?
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Well, since the octane rating for Premium Gas in California is 91, I would say yes! I do not like it, but, it is what it is. 
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Burning Brakes
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From: MSP
Ethanol not only burns slower, it contains less energy. You have to inject more of it to get the same bang, which effectively cools the cylinder for lower EGTs -- think water/meth injection, it's the same principle.
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From: nashville TN
Team Owner
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From: Hartford WI
The few E15 pumps I see here are 88 also. Might be 1 point above regular gas so why would I use that although it could? I'd use the highest octane I could whether it is E10 or E0.
Burning Brakes
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From: MSP
What discrepancy, exactly? Ethanol content is a separate concept from the fuel's AKI rating.
The AKI is the resistance to detonation. The ethanol content is simply the ethanol content. It's called out separately because older fuel systems (and certain engine blocks) cannot handle high concentrations of ethanol.
As a very high level explanation, ethanol has an AKI of about 99. When you blend ethanol into a fuel, it (usually) raises the AKI. That's why it's cheaper. If you start with an 85AKI fuel and blend it with 15% pure ethanol, you'll have a roughly 87AKI fuel.
The AKI is the resistance to detonation. The ethanol content is simply the ethanol content. It's called out separately because older fuel systems (and certain engine blocks) cannot handle high concentrations of ethanol.
As a very high level explanation, ethanol has an AKI of about 99. When you blend ethanol into a fuel, it (usually) raises the AKI. That's why it's cheaper. If you start with an 85AKI fuel and blend it with 15% pure ethanol, you'll have a roughly 87AKI fuel.
Drifting
Joined: Jan 2005
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From: Houston Tx
It’s more complicated than just splashing some ethanol into gas. Ethanol has high vapor pressure, so the gas you splash it into must be very low vapor pressure or it will be illegal. Gas with ethanol does not go through pipelines or leave the refinery with ethanol in it. The ethanol is added at the local terminal. The refinery sends “RBOB” or “CBOB” down the pipeline. The R or C stands for either reformulated or conventional (depending on whether you are in a high pollution city requiring reformulated gasoline). The BOB stands for blendstock for oxygenate blending, and the BOB’s for E15 ,must be even lower vapor pressure than the BOB’s for E10 so that when the ethanol is blended in, you won’t end up illegal on vapor pressure.
As far as octane, most of the comments are correct. Just because you have 15% versus 10% ethanol doesn’t guarantee that the E15 is higher octane than the E10. It all depends on what octane the BOB was when it left the refinery. The BOB is blended so that after the ethanol is added, it will end up as whatever the customer gas station wants to sell. So believe the octane posting on the pump rather than assuming that E15 is higher octane than E10, or E10 is higher than ethanol free.
As far as octane, most of the comments are correct. Just because you have 15% versus 10% ethanol doesn’t guarantee that the E15 is higher octane than the E10. It all depends on what octane the BOB was when it left the refinery. The BOB is blended so that after the ethanol is added, it will end up as whatever the customer gas station wants to sell. So believe the octane posting on the pump rather than assuming that E15 is higher octane than E10, or E10 is higher than ethanol free.
Last edited by LDB; Dec 28, 2022 at 06:25 PM.
Safety Car
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From: Norman OK
It’s more complicated than just splashing some ethanol into gas. Ethanol has high vapor pressure, so the gas you splash it into must be very low vapor pressure or it will be illegal. Gas with ethanol does not go through pipelines or leave the refinery with ethanol in it. The ethanol is added at the local terminal. The refinery sends “RBOB” or “CBOB” down the pipeline. The R or C stands for either reformulated or conventional (depending on whether you are in a high pollution city requiring reformulated gasoline). The BOB stands for blendstock for oxygenate blending, and the BOB’s for E15 ,must be even lower vapor pressure than the BOB’s for E10 so that when the ethanol is blended in, you won’t end up illegal on vapor pressure.
As far as octane, most of the comments are correct. Just because you have 15% versus 10% ethanol doesn’t guarantee that the E15 is higher octane than the E10. It all depends on what octane the BOB was when it left the refinery. The BOB is blended so that after the ethanol is added, it will end up as whatever the customer gas station wants to sell. So believe the octane posting on the pump rather than assuming that E15 is higher octane than E10, or E10 is higher than ethanol free.
As far as octane, most of the comments are correct. Just because you have 15% versus 10% ethanol doesn’t guarantee that the E15 is higher octane than the E10. It all depends on what octane the BOB was when it left the refinery. The BOB is blended so that after the ethanol is added, it will end up as whatever the customer gas station wants to sell. So believe the octane posting on the pump rather than assuming that E15 is higher octane than E10, or E10 is higher than ethanol free.
This is why I dont buy E10/E15 from the pump, well that and most of the E10 stuff is 87 E10 or 88 E10. I usually get either 91 or 93 and then add enough E85 to the mix to get the ethanol content mix up to E15. This way I start at 91/93 octane and then am raising it up to around 95-96 octane.
Team Owner
Joined: Jul 2004
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From: Hartford WI
This is why I dont buy E10/E15 from the pump, well that and most of the E10 stuff is 87 E10 or 88 E10. I usually get either 91 or 93 and then add enough E85 to the mix to get the ethanol content mix up to E15. This way I start at 91/93 octane and then am raising it up to around 95-96 octane.
Does it show reduced knock retard numbers when you scan the ECM?
Drifting
Joined: Jan 2005
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From: Houston Tx
This is why I dont buy E10/E15 from the pump, well that and most of the E10 stuff is 87 E10 or 88 E10. I usually get either 91 or 93 and then add enough E85 to the mix to get the ethanol content mix up to E15. This way I start at 91/93 octane and then am raising it up to around 95-96 octane.