I went 12 years burning 94 octane. I new that the compression ratio didn't support burning that high of octane but for some reason (besides having no ethanol) I thought it ran better, sounded better etc.
This spring I had to do a complete tear down for several reasons. I was blown away with the amount of carbon deposits on the piston and cylinder head. It became completely obvious that 94 octane was not good for this motor.
After the rebuild I put 87 octane in it and it ran ok. I thought the exhaust notes didn't sound quite as loud but I got better milage right away. Then I put in a tank of 89 octane and there was such a noticeable difference in sound, performance and even better milage that I have decided to stick with the 89 octane.
I run 87 , our 89 is 10% ethanol . In my car I don't get as good of mileage on the 89 so I run 87 in it also. Never tried it in my bike.
I'm getting better mpg since I grampsized mine , sprocket change helped too but that was before. My last 2 tanks have been 53 mpg + , combination hwy / city , thats up from 46-50. It runs like a scalded dog too.
Good topic. I have an 05-800 classic. When I got the bike 1 year ago the owner told me to use the best ( 91 ) i guess. I started to use it. Then I get on here and everyone said not to use it, so I switched to 87. Bike worked ok, lost a couple mpg and some pull but not too bad. I was talking to the dealer a month ago and he told me NOT to use anything other than 91. He said that small engines don't like ethanol and the only fuel doesn't have it is 91. He said and I looked on here about the use of ethanol and it worried me.I asked about carbon buildup and he didn't seem to think that would be a problem. I had carbon buildup last summer with 87 but I blamed that on slow driving, less than 50mph.
So for the last month I'm back on 91, and does the motor ever run good. Lots more power, better mpg #'s. So now I read this again and here I sit and wonder what gas I should be putting in the tank. I would love to get the right info from someone who should know and get this put to rest. I just want to do right by my bike.