Gearbox lubrication

[Andy24]

Hi
Anyone have any advice on the best lubrication for a 1924 roundtank gear box. I've seen varying ideas of semi fluid grease to various grades of oil. Anyone with personal knowledge of which is the better option I'd be grateful.
Thanks

[Steve.S]

BSA recommended Castrol D140 for the '30s 3 speed gearbox, and I imagine the 2 speed would be the same.
However, if you live in Antarctica you may want to use a lighter oil.
Some people recommend Thixotropic oil, but if you fit a sealed bearing, this shouldn't be necessary.