E15 gas?
Administrator
Joined: Mar 2001
Posts: 368,080
Likes: 24,732
From: In a parallel universe. Currently own 2014 Stingray Coupe.
C7 of the Year - Modified Finalist 2021
MO Events Coordinator
St. Jude Co-Organizer
St. Jude Donor '03 thru '25
NCM Sinkhole Donor
CI 5, 8 & 11 Veteran
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
Joined: Nov 2022
Posts: 910
Likes: 430
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?
Roadster Madness. 😠
Joined: Sep 2009
Posts: 6,289
Likes: 2,357
From: Ventura Co Ca
SoCal Regional Events Coordinator
St. Jude Donor '13, '20-'21
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. 
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Burning Brakes
Joined: Sep 2022
Posts: 1,202
Likes: 569
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.
Safety Car
Joined: Jul 2019
Posts: 3,829
Likes: 1,299
From: nashville TN
Team Owner
Joined: Jul 2004
Posts: 28,430
Likes: 3,280
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
Joined: Sep 2022
Posts: 1,202
Likes: 569
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
Posts: 1,942
Likes: 1,328
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
Joined: Nov 2011
Posts: 3,714
Likes: 343
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
Posts: 28,430
Likes: 3,280
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
Posts: 1,942
Likes: 1,328
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.