Knocking with 91

[Weiser699]

I bought a 2020 Sierra with the 6.2. I’ve noticed when running top tier 91 octane premium ethanol free my engine knocks bad at low rpm in high gear. When I add Lucas Octane booster, the knock goes away. I don’t have 93 where I live. Why would I have bad knocking on 91? What can I do about this without having to add octane booster? 

[swathdiver]

Change stations and or brands.  Ethanol in fuel is now used to control knocking.  Sometimes we think we're buying one grade of fuel when the tank is filled with something else, not supposed to happen, but it does.

[Vigilante375]

You might need to find a place with ethanol in it. 

 

Do you get gas from the same place?  If so, they may have a bad batch. 

 

If you get it from multiple places, then find a couple that have 10% ethanol in the gas.

[newdude]

Quote

 

Premium unleaded gasoline meeting ASTM specification D4814 with a posted octane rating of 93 — (R+M)/2 — is highly recommended for best performance and fuel economy. Unleaded gasoline with an octane rated as low as 87 can be used. Using unleaded gasoline rated below 93 octane, however, will lead to reduced acceleration and fuel economy. If knocking occurs, use a gasoline rated at 93 octane as soon as possible, otherwise, the engine could be damaged. If heavy knocking is heard when using gasoline with a 93 octane rating, the engine needs service.

Do not use any fuel labeled E85 or FlexFuel. Do not use gasoline with ethanol levels greater than 15% by volume.

 

 

I'd switch stations and avoid non ethanol 91 and see what happens.  If it still does it, you might need to stick with a booster.