87 gas will work this Model

More than likely yes being a newer car there may be a sticker some where or check the manual .. 91 and 87 have the same potential energy , 91 will not make your car go faster .

I had an RX and after experimenting with different octane ratings I found the running premium fuel over regular provided nothing but a drained pocket book, no mileage increase no performance increase. So run regular.

If there are no manufacturer's recommendations posted any where, regular 87 octane fuel will work just fine and cause no problems,

I’ve got a 2011 RX350, and have been using regular since I bought it in 2013. I’ve burned a couple tanks of premium along the way, and noticed no difference in drivability or mileage. If I haven’t ruined it after ten years, I don’t think I’ve got much to worry about.