For those of you interested in all the minute details that exist between regular, premium, ethanol additive and Top tier gas formulation. This video is packed with scientific studies resulting in real world results on the how's and why's and do's and don't for fuel in USA. Of particular note for myself, I have been using regular 87 octane Costco Top Tier gas in my '22 NX350h with no worries or concerns. In the video it's mentioned that higher octane rated fuels typically come with better, higher amounts of additives that provide increased cleaning of valves, injectors and piston rings and resulting improved mileage over a period of time used. Not just instant improvements to mileage, but over the course of a few months maybe of driving. I did the math for me and as I only do about 12,000 miles a year, it's only probably going to cost less than $200 a year to switch. Plus hopefully better mileage too. I'm going to make the switch. This is mentioned around the 14:00 minute mark.

 

I agree, In the case of the NX350h, not all the benefits will be instantaneous power and efficiency. The extra power from the engine using 91 octane will charge the traction batteries quicker and more efficiently. Which in turn will sometimes translate to better gas mileage, depending on your driving style.

 

So for you my 2 Starbucks a week estimate drops to 1 Starbucks a week

 

Higher octane would enable higher power at the cost of more fuel being able to be burnt.
So MPG would get worse, not better.

Plus you don't charge the battery because you have excess power: you ask the engine to give you power to charge the battery.
The only case you can charge more because of excess power is if you are braking and accelerating harder than what you could have done with 87 AKI: not really a scenario where MPG matters.

 

Well the EXPERT in the video pointed out clearly (from 18:00 to 18:45) that the engine will relearn it's mapping with higher octane fuel present, providing "better fuel economy and performance" as it takes advantage of the ignition enhancements. Horsepower and torque curves mapped out on a graph will indicate an improvement all across the rev range not just a blip at redline of rpm. These gains are available at all rpms and provide more hp and torque for equal amounts of lower grade 87 octane fuel. Your gas mileage will improve over a period of time with higher octane. That's proven and said from the expert. The only caveat is high octane gas costs more than regular.

High voltage battery conditioning is pre-mapped in software so there's a total disconnect here. The car will never recharge the battery to 100% as an example and never drain it to 0% either. One doesn't affect the other. Simply the ICE will run more efficiently with identical volumes of fuel when using a higher octane. This gain is obviously a minute amount nothing earth shattering.

 

The expert never mentioned higher efficiency.
He talked about performance, which is used to describe peak power.
That's what higher octane rating does: enable power power by avoiding knock.

Then the common horsepower vs RPM and torque vs RPM will not tell you anything about fuel efficiency.
For that you need the BSFC map: which is just fuel consumption in function of both RMP and torque.
But I know I am not talking to experts here.

Believe what you want, but don't try to convince others that your view is the truth.

 

One thing we all could agree on is that Lexus tuned the NXh to produce more power per volume of 91 octane gas compared to the same volume of 87 gas. How and where Lexus applied these extra power is unknown, but knowing Lexus, it is not wasted. This extra power may not be worth a couple of hundred dollars a year to some NXh owners since most are looking for high mileage and not improved performance. We could also agree that using 87 octane will not damage the NXh in any ways.