Suspension shops use/sell a lot of fork oil and only a couple of fork oil companies sell quality fork oil in 55 gal drums (at a huge discount over buying the fork oil by the liter) and those 55 gal drums are only available in 7w. Accordingly, suspension shops like Traxxion and GP Suspension use 7w oil to develop the shim stacks they sell in their homemade cartridges and that same weight oil should be used when the oil is changed.
Most of the bikes manufactured in Japan and Europe use 5w to develop their shim stacks so that is the oil that should be used in OEM forks if you are happy with the fork’s performance.
I felt my 2010 C14 had excessive compression damping but barely adequate rebound damping so their really wasn’t an option to use different fork oil to fix the excessive compression damping without screwing up the rebound damping. My solution was to buy ZX-14 forks off eBay and put them on the C14...which worked very well except the new forks had to be drilled to accommodate the ABS sensors.
