Not to jump in here but that’s how all modern vehicles engine management systems work no matter what fuel they have in them. They are constantly trying to run on the edge of detonation for maximum efficiency and they do that by advancing until knock is detected and then backing off. Basically rinse and repeat. It’s not bad for them, it’s just how they are designed. Where the concern would be is if the computer could not control the detonation from pulling back the timing which could potentially be a risk for a turbo engine in some circumstances although most stock engines these days are really designed with the fact in mind that any octane level could be used in them no matter what the fuel lid sticker says.

 

I believe if an engine is design for 91 octane, the timing would stop advancing if you use 91 octane, not repeatedly go thru the detonation cycle. From the above article, Sounds like Lexus delay the timing movement to slow down this cycle when using lower octane gas. Detonation in an engine is never good, intentional or other wise.

 

I have read posts regarding this issue, and still not sure if the 2020 nx300 hybrid needs 87, 89 or 91 octane. The manual refers to Research Octane Number 91. Found a formula R+M/2 which is 89. Article also states that particular formula is not applicable in the US and Canada.
Don't mind using 91, but the manual seems to indicate 87 or higher is ok.

 

The owner's manual for my 2020 NX Base clearly states that "If the octane rating is less than 91,damage to the engine may occur and may void the vehicle warranty."

I am way beyond the warranty period and at 109k in my wonderful well-kept NX.

Although in NJ I'm not supposed to self-serve at the pump, I ALWAYS do it myself (for several reasons). On my recent fill-up 3 days ago, the attendant beat me to it, and grabbed the hose handle before me. I'm certainly not going to fight them.

I didn't realize until 1 minute later, that they were putting 87 octane in, when my vehicle calls for 91 (they forgot to ask, I forgot to watch). I made a decision to let it go, and perform an experiment.

Thus far, I've consumed about 25% of the tank and haven't noticed any difference (or pinging). I don't haul anything, usually have no passengers, and no more than perhaps 100 lbs of additional items (groceries, etc.) in the car. The last few years I've been driving at/below the speed limit most of the time. I don't jackrabbit, and I'm never in any rush to get to my destination. Most of my driving is on level ground (no hills or mountains).

ASSUMING that I get thru this tankful with NO noticeable difference, and no new sounds (pinging). If that happens, do you think it would be okay to continue to JUST use 87 octane? Will the PINGING be the very first sign that my engine is not liking the lower octane? Worded differently, as long as I don't hear the knocking, am I NOT doing any damage to my engine?

Another alternative might be to fill my tank half and half 87/91, but even if that is acceptable, honestly, I just don't have the patience for it and would rather just put in the 91.

 

FOR Regular ICE Vehicles Only:

Personally, if I have a doubt or question about something, I just go with what I know FOR SURE is recommended, erasing all doubt.

But that’s just me and we ONLY use Premium gas for our Lexus vehicles that recommend premium or atleast 91 octane and try to use Top-tier gas.

I’ve seen / read regular owners, mechanics and so-called experts saying you can absolutely use 87 octane on our turbo engine, with no issues.

Likewise, I’ve seen the same type of people say the same for 91 or above octane that would never use any fuel that’s less than 91 octane.

If it works for you, great. You do you and I’ll do me.

To each their own.