A couple of years ago I checked my trailer hubs,similar size to mini hubs, and the bearings looked a bit dry i had been using Castrol moly grease, had look on the tub and it states that moly grease should not be used for auto wheel bearings. I do not remember this warning when Castrol used tins before the plastic tubs. I had a think about my previous comment on straight thirty making the slides stiffer,I suppose its because the multigrade iI normally use is lower viscosity. I use 32 hydraulic oil on both my Colchesters,as thats the specified oil and is in use for a long time in the gearboxes/headstock. I cannot why there is objection to using good multigrade oil for Myford bearings, the lubrication system is total loss so the bearing gets a constant feed of fresh oil,if there is any debris in the oil it goes to waste and does not recirculate.Automotive and motorcycle gearboxes of the 1960s tended to use motor grade oils,and minis and others used the engine oil to lubricate the gearbox,our lathe headstocks are a similar technology to those days so multigrades should be ok,there used to be a saying any oil (except EP) is better than no oil. There has been a trend to using thinner oils in gearboxes as speeds increased. From 1950 to 1960 the gear box oil on villiers motor cycle engines changed from sae 140 Castrol D ,to 90 and then to 30 ,