Re: 91 frok oil capacity
not at home to look up the volume in the manual, but IIRC the stock oil is Honda SS7, which is 5W, not 7.5. The other Honda oil, SS8, is 10W, there's no Honda fork oil I'm aware of that's 7.5W. Upgrading to 12.5 isn't a bad idea, but straight 15W is probably going to be too stiff. I tried it once, and went back to 12.5W.
Many will argue that setting oil level by distance measurement below the top of the fork tube is preferable to measurement by volume, if neither figure is reported by the time I get home I'll post both methods from the manual when I get a chance.