I have been told to use octane rating of 93. Manual states 91. Would ethanol free gas rated at 90 octane be better for the engine as it does not contain ethanol?

 

If the manual has 91 why not go with that?

In the past using a higher octane doesn't necessarily bring you anything extra but just cost more.

You want to void your warranty by using a lower octane go for it. It might cause knocking and damage the engine.

 

Ethanol or no ethanol, I would never put gasoline below the recommendation in my motorcycles outside of an emergency.

I have heard spark knock even at altitude with 91. If I could buy 93 at the pump, I would, but we don't have it here.

 

I always use 93 octane. You have spent a lot on your bike so go with the best.

 

Go with the recommendation of MoCo