First let me say Hello as I am a new member here and just started rideing again after 20 years. To my luck I bought a VTX 1300c and now at 20k on it I would like to change out the final drive oil. I was looking at going with Royal Purple 75-90wt. This is fully synthetic and avaible at my local ABC Auto parts. Any thoughts on this or is there another oil that is perfered?