Fork oils can have lots of variability in actual viscosity for any 'claimed' weight (and they can claim grades that don't even exist!). It's really the KV40C that's closest to real life flowing conditions, so pick whether you feel you want to go lighter or stiffer and pick by actual stated viscosity at 40C for any product
. I wanted to go super light for my Griso front end and went with Puraline HPXR 2.5W....it's stated at 6.7cst viscosity (KV@40C). Motul 5W is factory recommended and 18cSt (that's almost three times the 2.5W viscosity). Castrol 5W is 15 Cst....you can see from Castrol literature how the KV40C changes with grade - I wouldn't go 20 as that's very heavy viscosity & unless you live in the arctic/Atakama, there's no need for a summer and winter grade selection.
