Originally Posted by Crankycrank

What brand and model freehub? They don't all use the same viscosity lube. Can't think of any that 20-40wt oil would be the best weight lube for. Too thin in most cases. It works but can tend to seep through the seals leaving you with no lube. Also, if you ride in extreme heat or cold you may need to adjust the viscosity to suit the temps. Be prepared for lots of differing opinions on this.