85-86 octane Gasoline
 

I've seen very low octane gas when in Wyoming and New Mexico. Will this hurt my car?

Lexus specifies a minimum octane of 87. I doubt that a single fill up or an occasional rare fill up with 85 octane would do harm to the engine, but I would be reluctant to use less than 87 octane on a regular basis. If the octane rating of the gas you are using is not sufficient, the first sign of that would likely be that you would notice the engine knocking.

Areas at higher altitudes usually sell lower octane gas because the octane you are seeing is equivalent to the 89 octane used at lower altitudes, due to the density altitude (for a non-boosted engine). That is to say, an effective lower compression (due t the higher altitude) results in a lower fuel octane requirement.

It may affect fuel efficiency slightly, but that should be it. The engine is computer controlled and adjust for variations in octane automatically and engine 'knocking' is not likely.