I don’t know anything about the additives for fuel. I do suspect that they could have an affect on O2 sensors. You remember the problem with lead and O2’s?
Maybe that is why the Nissan manual was against the additives.
Deposits in the combustion chamber can for sure cause pre ignition. Most of the time you would not know, because the knock sensor hears it before we do and offsets the timing.
If you can feel a definite increase in performance with premium gas, then it is the result of the knock sensor NOT pulling timing back. It would be letting the engine fire when it is supposed to rather than having it’s timing retarted by the knock sensor.
I don’t know of any way to clean deposits out of the engine without pulling the heads. Maybe someone on here knows of some miracle additive that will remove deposits.
There is not much truth in advertising these days, so it is hard to sort through all of the products on the market.
For sure all of these vehicles left the factory expecting to just run regular fuel. California vehicles used to have extra pollution equipment, but I don’t know if there is any difference now.
One of the things I have done to increase octane is to blend some E85 with regular gas. I would put in 12 gallons of regular and 8 of E 85. That put me near 100 octane for race day. It is kind of a PITA for a daily driver though, unless you only live one mile from work like I do.