Accidentally put 89 instead of 91 in 2020 glc63s
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Junior Member
Joined: Nov 2020
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2020 glc63s coupe. 2021 mach e awd. 2016 camaro 2ss.
Accidentally put 89 instead of 91 in 2020 glc63s
I've read it will adjust with no permanent damage and readjust back, but will I need to reset the ECU?
Some people said you'll need to unplug the battery after you fill it up with 91 again, to reset the ecu. Is that true?
How worried should I be? Should I constantly fill up every quarter tank with 94 to counteract it?
About 2/5 of the tank is 89, 3/5 is 91.
Some people said you'll need to unplug the battery after you fill it up with 91 again, to reset the ecu. Is that true?
How worried should I be? Should I constantly fill up every quarter tank with 94 to counteract it?
About 2/5 of the tank is 89, 3/5 is 91.
Junior Member
Joined: Oct 2020
Posts: 63
Likes: 23
From: Laguna Hills, CA
W204 C63 AMG
Just take it easy on the full throttle romps. Not sure the highest level of octane in your area, but once down to 1/2 a tank, top off with 93.
No need to reset the ECU. It will adapt rather quickly.
No need to reset the ECU. It will adapt rather quickly.
Out Of Control!!
Joined: Nov 2018
Posts: 11,429
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From: San Francisco Bay Area
2019 C63CS
You will be fine. The minimum octane rating is indicated on the fuel door. I believe it's 87 AKI. You can use that as a temporary measure, but it's recommended to avoid full throttle and sudden acceleration until you can fill the tank with at least 91 AKI again. The risk of knocking is increased under heavy engine loads. The ECU can only retard so much, but the engine will protect itself if it detects knock, even reducing power if necessary. Adding octane booster to a full tank is essentially pointless, because it won't be mixed well. If you use octane booster you should pour it in first and then fill it so it mixes properly.
Last edited by superswiss; May 22, 2021 at 11:20 PM.
Super Member
Joined: Aug 2019
Posts: 881
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AMG GLC 63s Coupe
Octane booster can burn up o2 sensors.
Don't worry about it. If the temps in your area are on the cooler side, it is unlikely anything will happen. If it is 100f outside then I wouldn't go looking for a race until you put some good gas in it. When you get to 1/2 tank, fill it up with the best you can find.
Don't worry about it. If the temps in your area are on the cooler side, it is unlikely anything will happen. If it is 100f outside then I wouldn't go looking for a race until you put some good gas in it. When you get to 1/2 tank, fill it up with the best you can find.
Junior Member
Joined: Aug 2016
Posts: 22
Likes: 1
From: San Antonio, Tx
2013 C63 AMG Coupe
Car is completely toast.
Burn it to the ground and collect insurance money....
(It's fine to run on regular, no harm will come to it at all - it has knock sensors - don't add anything to it like the above suggested - just drive it and stay out of the deep boost if you can).
Burn it to the ground and collect insurance money....
(It's fine to run on regular, no harm will come to it at all - it has knock sensors - don't add anything to it like the above suggested - just drive it and stay out of the deep boost if you can).
Member
Joined: Jun 2018
Posts: 226
Likes: 47
From: N. Maryland
2024 GLE 580
Car is completely toast.
Burn it to the ground and collect insurance money....
(It's fine to run on regular, no harm will come to it at all - it has knock sensors - don't add anything to it like the above suggested - just drive it and stay out of the deep boost if you can).
Burn it to the ground and collect insurance money....
(It's fine to run on regular, no harm will come to it at all - it has knock sensors - don't add anything to it like the above suggested - just drive it and stay out of the deep boost if you can).
