use whatever octane level your owners manual says to use.

 

I believe here in Kalifornia, you can't get gas without ethanol. I believe it is mandated by law.

 

We get to have 91 Octane with no ethnal in it for the winter mounths as the Snow sleds don't do good with the ethnal. 2 stroke engines just don't take to the ethnal.

This past weekend I drove 300 mile with the 50/50 mix of 89 and 91. I got 18.6 MPG.
On strate 89 I was only geting 15.7 Will be filling the tank today and going with 91 only to see what MPG I can get.