Join Date: Jul 2019
Location: South Carolina Upstate
Just for curiosity's sake, over the past couple of weeks I ran 2 tanks of 89 octane through my Z650, then 2 tanks of 87. I really couldn't tell any significant difference in the power delivery between the two, but gas mileage was a different story. With the 89 octane, I averaged a fraction over 55 MPG. Using the 87, the mileage was a fraction over 58 MPG. Important to note, the trips made were identical over those two weeks other than maybe a couple of around-town jaunts -- overall, a mixture of in-town and highway trips that I take on a weekly basis -- and being conscious of the fact I was trying to make a valid comparison I took care to keep my riding style consistent over the entire period. Doesn't prove anything, of course, but it surely tends to support the manual's specification of 87 octane fuel.