Some of you may remember two years back I spent the summer testing fuel stations by brand, octane, and calculated fuel mileage for highway use.
I found by far the best was a BP near my house using 89 octane.
Higher octane as we all know is not more explosive but has additives to prevent pre-ignition (spark knock)..the less spark knock, the more power and better fuel economy you will have.
I noticed no difference between 89 and 93 but had a substantial loss in mileage in 87...regardless during my testing I had zero audible spark knock.
Today I went back to the station and filled up with 93. I will see if that makes a change.
Riding today I did notice I could also hear it in 3rd gear at almost exactly 3000 rpm. It still sounds like spark knock to me.
Now a side note. Somewhere around my trees or windshield I hear a small rattle, like a washer on a loose bolt. It MAY be that noise being vibrated at the frequency produced around 3000 rpm but this is speculation. The noise behind the windshield is the windshield lock lever but it only makes a noise at lower speeds and a lower RPM...
I may slip a rubber hose over the leaver to dampen the windshield lock if the higher octane does not fix the noise.
I dont care about the windshield lock noise as I know it will hurt nothing but spark knock is bad for engines.