I'll check the manual tomorrow, but in the meantime... My '23 NX450h+ manual said to use premium, which I always did. I'm assuming it's the same for the '26 RX450h+, but wouldn't it be nice if it's not.

Virtually all Lexi now require 91 Octane Premium fuel.
The UX's use 87 Octane Regular. RX and NX 350h's can use 87 but recommend 91
All 450h+ and 500h require 91.

Thanks

Incorrect. The RX500h requires 91, but Lexus only recommends 91 in the RX450h+ The NX450h+ is the same, 91 recommended but 87 ok.

Personally, I run 91 in our RX450h+

From the RX450h+ manual.

Thanks

With my RX450H+, at most 50 %, and more likely 30 %, of my entire odo miles (~21 K so far) are gas-miles, as my commute and in-town miles are 100 % electric.

So I always choose to put Shell 91 octane in the tank, because of the additives in it that have been proven in multiple evaluations (see youtube and other sources) to significantly reduce build-up of gunk in engines over time. So in essence, I pick the Shell 91 octane (1) for the maximal additives available in the 91 octane, rather than the specific octane itself (2) I use so little gas that the extra expense over 87 octane doesn't really matter.