15% ethanol in LT2
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 952
Likes: 337
From: Cedar Rapids IA
15% ethanol in LT2
I live in Iowa so E85 is readily available, I also have 91 octane no ethanol fuel available, no 93 ethanol free here. I used to put 3 gallons of E85 in the tank of my 19 Z06 along with the 91 and it definitely made a difference in performance, but that was a supercharged motor. Kind of curious if anyone is doing this with the LT2 in the C8 and if it makes more noticeable power. Would be much cheaper to do than the many bolt ons that only yield a few HP, get the same increase, and keep warranty intact. I will for sure be trying it but hopefully someone else can weigh in as to whether it helps at all. My Stingray is only a month old so no flex fuel conversion until warranty is expired and maybe not then depending on cost.
Instructor
Joined: Jan 2022
Posts: 120
Likes: 96
From: New York
My car has a SC and Callaway told me do not use any flex fuels . I always splash my other cars with a few gallons , MB and dodge ram and the performance is noticeable as well. Been doing it for several years and no issues .
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 952
Likes: 337
From: Cedar Rapids IA
The fuel I have available in the mixture would meet octane requirements and not exceed 15% ethanol if I put 3 gallons of E85 in the tank. Actually with the octane boost of E 85 it would exceed 91 octane , don't know where it would end up but over 91 for sure. I just wonder if the ignition/fuel maps would allow the LT2 to take advantage of the increase to make any more HP. In the Fall I would cease adding E85 to purge the alcohol before Winter storage.
Drifting
Joined: Feb 2000
Posts: 1,916
Likes: 109
From: Crystal lake Il
2022 Corvette of the Year Winner -- Modified
2021 C4 of the Year - Modified Winner
Burning Brakes
Joined: Aug 2023
Posts: 1,031
Likes: 852
From: West NY
This adding E85 or converting to E85 doesn't make any sense in a stock LT2. There is no benefit to raising the fuels octane in and engine that has been engineered to run on 91 octane. Ethanol has a lower energy content vs gasoline to the tune of 33% less btu. So using E85 will take 30% more fuel to make the same power as gasoline. Some benefit from running E85 in engines that introduce fuel into the intake tract because of the cooling effect of the incoming air, but the LT2 is direct injected, so no benny there. The LT2 would only benefit if you...1, increase the compression ratio from11.5:1 to 13.5:1 or more. 2, install some sort of forced air induction as in turbo or super charging that would require much more fuel of a higher octane. Putting E85 in a stock LT2 is just really stupid and not worth the cost to take away power. Dumb.
Last edited by Acpantera; Jun 30, 2024 at 01:03 PM.
Drifting
Joined: Feb 2000
Posts: 1,916
Likes: 109
From: Crystal lake Il
2022 Corvette of the Year Winner -- Modified
2021 C4 of the Year - Modified Winner
Interesting observations, in the thread one of the fastest C8s in the country noted they picked up 12hp/9ftlbs of torque without a tune @ 25% E, you can see the dyno sheet in the thread
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Burning Brakes
Joined: Aug 2023
Posts: 1,031
Likes: 852
From: West NY
Racer
Joined: Feb 2020
Posts: 387
Likes: 576
From: Philly
Drifting
Joined: Mar 2016
Posts: 1,731
Likes: 496
From: Glenelg MD
I'd suggest that simply ensuring your tank is as full as possible during the winter months will reduce the amount of moisture-laden air that gets pulled in with every day's heat/cool cycle.
Thread Starter
Burning Brakes
Joined: Jun 2001
Posts: 952
Likes: 337
From: Cedar Rapids IA
I started doing that and keeping a reduced fill on my C7 after experiencing gas gauge issues. One dose of Techron fixed it but a bit of preemptive planning is always better than a repair being required later. Apparently the alcohol somehow affected the sender in the tank and caused it to become inoperative. Some folks had to drop the tank and replace the sender unit.
BTW, in the C7 it was suggested to keep the tank at 1/4 during storage to allow the gauge to work better after Winter storage, not sure if the C8 is the same. I suspect this forced the gauge to have an output voltage change when the car was woke up and the tank filled after sitting for an extended period. I never had an issue after following the 1/4 tank and no ethanol during storage recommendation.
BTW, in the C7 it was suggested to keep the tank at 1/4 during storage to allow the gauge to work better after Winter storage, not sure if the C8 is the same. I suspect this forced the gauge to have an output voltage change when the car was woke up and the tank filled after sitting for an extended period. I never had an issue after following the 1/4 tank and no ethanol during storage recommendation.
Last edited by GS583; Jul 1, 2024 at 09:27 AM.
Melting Slicks
Joined: Aug 2000
Posts: 2,390
Likes: 1,166
From: Early 2020 Z51 Coupe, Original Owner, Ahwatukee Foothills, AZ
That's right. Performance goes UP, mileage goes DOWN. I use a great station that has E85 as a minimum, it averages 90%.
Have the E85 Flex/Fuel Global B Tune with 484 rear. Nothing but pleasure
Excluding 6Speeder, If your a worry warranty boy, I don't give a Flyin F.
Have the E85 Flex/Fuel Global B Tune with 484 rear. Nothing but pleasure
Excluding 6Speeder, If your a worry warranty boy, I don't give a Flyin F.
Last edited by ArizonaZ06; Jul 1, 2024 at 02:50 PM.
Race Director
Joined: Jan 2014
Posts: 10,709
Likes: 7,099
From: Fulshear, TX
GM states in the owner's manual that up to 15% ethanol has been approved for use, with that said, a lot of us are running 20-30% to pick up that extra octane and the engine loves it. The sweet spot seems to be ~95-octane with the factory ECU & tuning. I've provided my E85 spash-blend calculator to a few guys, including @teddyca, so if anyone else wants it please just PM me your email address. I have it setup for splash-blending with both 91 E0 as the base fuel, and 93 E10, depending on your area.
To the OP in Iowa, certain Kum & Go locations (soon to be rebranded to Mavericks) do offer 93 E10 at the pump.
I just made the drive from TX to far northern Minnesota in my Jeep and ran E15/Unleaded88 the entire way, and averaged better than expected MPG due to the slight increase in octane/knock quench preventing the ECU from pulling timing as it typically does when running regular 87.
To the OP in Iowa, certain Kum & Go locations (soon to be rebranded to Mavericks) do offer 93 E10 at the pump.
I just made the drive from TX to far northern Minnesota in my Jeep and ran E15/Unleaded88 the entire way, and averaged better than expected MPG due to the slight increase in octane/knock quench preventing the ECU from pulling timing as it typically does when running regular 87.
Melting Slicks
Joined: Aug 2000
Posts: 2,390
Likes: 1,166
From: Early 2020 Z51 Coupe, Original Owner, Ahwatukee Foothills, AZ
GM states in the owner's manual that up to 15% ethanol has been approved for use, with that said, a lot of us are running 20-30% to pick up that extra octane and the engine loves it. The sweet spot seems to be ~95-octane. To the OP in Iowa, certain Kum & Go locations (soon to be rebranded to Mavericks) do offer 93 E10 at the pump
And to make things a more convoluted when the 2020 C8 arrived, if you were lucky enough to own one, the C8 owner's manual clearly stated that Required Recommended Fuel was 93 octane. The LT2 engine has not changed since it's Day 1 debut. Only the manual verbiage was slightly changed and got GM around their octane warnings by manipulating their wording. Truth of the matter as stated in their 2020 and 2021 owners manual, "If unavailable, 91 May be used, BUT with Reduced performance and fuel economy".
Some associated C8 owners are not interested in maximum engine performance and some are, that's why we are here on the C8 Tech/Performance Discussion.
Le Mans Master
Joined: Jan 2006
Posts: 9,049
Likes: 664
From: Norcal
My CA car with 91/E85 blended to about 95 octane seems to be happy. We don't have any Kum and goes here in CA. They are called something else and they don't sell gas
. I remember a few years ago while travelling for work I seen one of these stations and about lost my ****. I had to send all my buddies a picture. The kid in me couldnt get over that name. I walked in and was disappointed. 
. I remember a few years ago while travelling for work I seen one of these stations and about lost my ****. I had to send all my buddies a picture. The kid in me couldnt get over that name. I walked in and was disappointed.
Racer
Joined: Feb 2020
Posts: 387
Likes: 576
From: Philly
That's a great help to members, nice post!
And to make things a more convoluted when the 2020 C8 arrived, if you were lucky enough to own one, the C8 owner's manual clearly stated that Required Recommended Fuel was 93 octane. The LT2 engine has not changed since it's Day 1 debut. Only the manual verbiage was slightly changed and got GM around their octane warnings by manipulating their wording. Truth of the matter as stated in their 2020 and 2021 owners manual, "If unavailable, 91 May be used, BUT with Reduced performance and fuel economy".
Some associated C8 owners are not interested in maximum engine performance and some are, that's why we are here on the C8 Tech/Performance Discussion.
And to make things a more convoluted when the 2020 C8 arrived, if you were lucky enough to own one, the C8 owner's manual clearly stated that Required Recommended Fuel was 93 octane. The LT2 engine has not changed since it's Day 1 debut. Only the manual verbiage was slightly changed and got GM around their octane warnings by manipulating their wording. Truth of the matter as stated in their 2020 and 2021 owners manual, "If unavailable, 91 May be used, BUT with Reduced performance and fuel economy".
Some associated C8 owners are not interested in maximum engine performance and some are, that's why we are here on the C8 Tech/Performance Discussion.
However, if that is true....the 2020 and '21's are potentially the faster C8s.
Just stirring the pot gents !
Race Director
Joined: Dec 2006
Posts: 12,317
Likes: 2,868
From: Fort Worth, Texas
GM states in the owner's manual that up to 15% ethanol has been approved for use, with that said, a lot of us are running 20-30% to pick up that extra octane and the engine loves it. The sweet spot seems to be ~95-octane with the factory ECU & tuning. I've provided my E85 spash-blend calculator to a few guys, including @teddyca, so if anyone else wants it please just PM me your email address. I have it setup for splash-blending with both 91 E0 as the base fuel, and 93 E10, depending on your area.
To the OP in Iowa, certain Kum & Go locations (soon to be rebranded to Mavericks) do offer 93 E10 at the pump.
I just made the drive from TX to far northern Minnesota in my Jeep and ran E15/Unleaded88 the entire way, and averaged better than expected MPG due to the slight increase in octane/knock quench preventing the ECU from pulling timing as it typically does when running regular 87.
To the OP in Iowa, certain Kum & Go locations (soon to be rebranded to Mavericks) do offer 93 E10 at the pump.
I just made the drive from TX to far northern Minnesota in my Jeep and ran E15/Unleaded88 the entire way, and averaged better than expected MPG due to the slight increase in octane/knock quench preventing the ECU from pulling timing as it typically does when running regular 87.
Burning Brakes
Joined: Aug 2023
Posts: 1,031
Likes: 852
From: West NY
Have been running 88 octane/E15 from QT in all my DD’s and it helps prevent knock as well as makes a little more power because of more advanced timing which results in better mpg when cruising from a more efficient burn I believe. It’s also cheaper than regular 87 octane.