The metal plate on my S-L manual windlass
says "Fill with oil
grade SAE 140 or nearest"
I have not been able to find this single
, although I have found SAE 85W-140 multi-weight.
Interestingly, the manual I downloaded from SLSpares says use SAE EP80. (No mention of SAE 140)
What do you use/recommend for your S-L windlass