Correct fork oil? 1990 GSXR 1100

[ACTAngler]

Trying to work out correct fork oil for my 1990 GSXR1100 (conventional forks). Local Suzuki shop reckons 10W, but Haynes manual says 5W for 1989 and 1990. It gets even more confusing in the manual with quantity...

Can someone please set me straight?

Thanks in advance.

[evilkarl]

I've tried them all and never noticed any difference. Are you putting the old springs back in?
I've done plenty of Oilers folks over the years and most reciently used 20w motorcross oil, worked well.

[ACTAngler]

yeah, standard springs for now.

[80s freak]

Easyiest way is older usd forks are normally 5w. right way up are 10w.