I am gonna use this thread to post results of a practical comparison between those two fuels and the effects on performance they had on my 2015 IS350 RWD f sport (with blue f sport air filter). Everything else is stock on the car. I am also gonna reset the ECU ever time I fuel the car.

This is an offshoot thread that originated here https://www.clublexus.com/forums/is-...threads-8.html

this was the original post https://www.clublexus.com/forums/is-...l#post10370809 that prompted me to create this thread.

I am gonna post data logs from my BlueDriver OBD logger. Currently I am in the final stage of collecting base line for E0 91 fuel.

Absolutely agree. I am not making any claims on the repeatability of the results
And even a robot will not let you control env. parameters like air pressure and temperature, road conditions, traffic patterns and traffic lights patterns.
Nonetheless, I will attempt to test two cases - low RPM high gear WOT pull and high RPM low gear WOT pull. Those are slightly easier to repeat, because you just have to stomp on the pedal as quickly as possible.

my primary interest is in how ecu will retard timing for 87. Mpg results are less of interest, especially because I am not sure I wanna run 87 for more than 1-2 full tanks.

Okay, so here is the data.
Conditions were about the same for both sets. It was dry and about -2 to 3C outside temperature.

I did two types of pulls - high RPM pulls (3rd-4th gear from 65-74 mph to 85, from 0 to 80mph, WOT) and low RPM pulls (from 70-ish mph in 8th gear, WOT).
There were roughly about 20-24 pulls for each type of fuel (10-12 for low RPM and the same for high RPM).
I simply clumped together multiple pulls on the graphs, so I could look at all the data for the same fuel + type of test (low rpm or high rpm).
Also, I added averages, which are shown as thick marks to the right of each plot.

Low RPM data sets (left - 87, right - 93)
It is quite clear that the average timing for 87 was 10 deg, while for 93 it was 15 deg. RPMs (shown in blue *100) are about the same on average. Green value of 69 indicates that the throttle pedal is being pressed to the floor, but without activating that accelerator button at the end of the pedal travel. Pressing through that button would give 72 or so).

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High RPM data sets (left - 87, right - 93).
The average timing for 87 was 22 deg, while for 93 it was 24.5 deg.

I thought it was just odd that 93 octane has the timing cut, while demonstrating that the timing on average is higher than what 87 showed, while producing more power. My guess is that it does produce more power and enough of it to trigger TC. Matt Farah, Savagegeese and Everyday driver did mention that TC sucks life out of the car. So, it looks like it is a good theory for why timing gets cut on that 93 highrev graph. It is time to test it.

You getting any info on pre-det and knock? Pushing the engine hard with low octane (anti-knock) would show the timing pulled back like that. I haven’t bothered to look around and see if you can pull data from the Lexus knock sensors. If the engineers say use 91+ I use 91+. Having seen what knock and pre-det does to engines.

I dont, because my OBD2 scanner does not read that parameter. But I thought that timing will get affected by the ECU, when it detects knocking, so I might as well just use that.

Modern ECU will not let the engine knock for long. Repeated signals from one of the knocking sensors will be enough for the ecu to cut the timing sufficiently to stop the knocking. Besides, in the official manual, it is said that occasional knocking sounds should be of no concern. In other words, they know that the Ecu will keep the motor safe, and they also know that it is impossible to prevent the knocking in 100% of the cases without compromising performance.
But if you stop it immediately right after it starts, the engine will be fine long term. It is not the knocking that destroys the engine, but rather HOW LONG you have that condition in relation to how long you run the engine.

I am not planning on running it on 87 anyway. It was just an experiment (allowed by the manual, btw).

Haha true. Though with enough boost pressure you really only need knock for a short period.

these engines have decently high compression, so that window is a lot smaller compared to older engines with mild to medium compression. I do trust Toyota’s engineers enough to not worry. Just curious to see if you had the data. My scanner doesn’t show it either.

With enough boost pressure you will only get exactly one knock.... before the engine eats itself.
Aka terminal boost pressure )