91 octane?
Thread Starter
Heel & Toe
Joined: Aug 2022
Posts: 24
Likes: 5
91 octane?
Unfortunately, I live in a state (AZ) where 93 octane gas isn't available. We only have 91 octane here. From what I understand, 91 octane can possibly cause detonation issues for spirited driving, especially in the heat of the summer.
For those of us using 91, has anyone experienced any issues?
I know I can mix in a couple of gallons of high octane racing fuel (such as Sunoco 100 which is available here), and so I may do that in the summer, but I was curious as to anyone else's experience or approach, if any! 🫣
For those of us using 91, has anyone experienced any issues?
I know I can mix in a couple of gallons of high octane racing fuel (such as Sunoco 100 which is available here), and so I may do that in the summer, but I was curious as to anyone else's experience or approach, if any! 🫣
Pro
Joined: Jan 2023
Posts: 615
Likes: 653
Absolutely zero issues with 91 octane fuel. I live in CA in the valley where it routinely is over 100 in the summertime. Nothing but 91 available where I live. LT6 adjusts timing automatically to the octane. No need for additives of any kind. Just drive it and rip on it, you won't notice a thing.
Race Director
Joined: Feb 2011
Posts: 14,724
Likes: 5,601
From: AZ
Live in AZ high country, which would minimize possible detonation, but you should have no worries. GM knows half the country only has 91 and the engine is fine with that. 93 would be better and a little more of the rated power but no mechanical issues using 91. In the Utah high country their premium is 90 octane.
Thread Starter
Heel & Toe
Joined: Aug 2022
Posts: 24
Likes: 5
Live in AZ high country, which would minimize possible detonation, but you should have no worries. GM knows half the country only has 91 and the engine is fine with that. 93 would be better and a little more of the rated power but no mechanical issues using 91. In the Utah high country their premium is 90 octane.
Thanks for the info. Just want to make sure the LT6 can handle it. I miss the days when I was back east and had access to Sunoco Ultra 94.
Pro
Joined: Jan 2023
Posts: 615
Likes: 653
GM knew the car would be running 91 only in some states. There is a slight performance drop. You won't get the full 670hp, probably losing anywhere from 10-30hp depending on who you talk to. 91 is safe for the entire life of the engine, period. GM specifically does not recommend octane boosters because the additive chemistry is unpredictable, it's possible emissions can be contaminated, results vary by brand, etc. Best bet is to 50/50 mix of 91 pump and 100 UNLEADED race gas if you can find it but honestly for regular street bubbas like me I doubt it's noticeable.
Everything above is what AI says so take it with a grain of salt, but it sounds pretty good to me.
Everything above is what AI says so take it with a grain of salt, but it sounds pretty good to me.
Drifting
Joined: Oct 1999
Posts: 1,675
Likes: 493
From: Corrales NM
You can cheat the system to get 93 octane if you can find stations that sell 91 octane ethanol free gas and E85. I have both in my area. With low fuel in tank fill with 91 octane non ethanol. Drive until you have used 3 gallons, then fill up with E85. You'll have 14% ethanol in tank (max allowed by GM is 15%) and you'll have approximately 93 octane equivalent fuel. A pain in the butt to do but it does raise the octane.
Race Director
Joined: Feb 2011
Posts: 14,724
Likes: 5,601
From: AZ
The Love's gas station off I10 east of the Wild Horse Pass exit does have 100 octane unleaded. When I drive the Wild Horse Pass tracks, i mix in about 5 gallons of the 100 to bring the tank octane up to about 94 for track days. Last time I was there $9 per gallon.
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Thread Starter
Heel & Toe
Joined: Aug 2022
Posts: 24
Likes: 5
Race Director
Joined: Feb 2011
Posts: 14,724
Likes: 5,601
From: AZ
I am used to the power loss. Up here at elevation I lose about 12% of the power you have down there, both running 91 octane.
As an example of the altitude impact, in my HCI C6Z at 6500' elevation I trapped 176 MPH in the mile. At 2300' elev. I trapped at 188 with the same setup (less 75 # as I took the passenger's seat out to haul track rear tires 400 miles. I didn't want the passenger's outside mirror blocked for that long a drive.
As an example of the altitude impact, in my HCI C6Z at 6500' elevation I trapped 176 MPH in the mile. At 2300' elev. I trapped at 188 with the same setup (less 75 # as I took the passenger's seat out to haul track rear tires 400 miles. I didn't want the passenger's outside mirror blocked for that long a drive.
