Don’t think it really matters what oil you use, any oil is better than none. I use chainsaw oil on the slideways it tends to cling and my garden machinery supplier usually has it on offer, it seems that the local tree surgeons no longer use it, they have found a cheaper alternative, sunflower oil from the local supermarket. I also use chainsaw oil for lubricating the loco, doesn’t get flung off of the motion when running as much as normal oil does.

Whatever grades you use, within a sensible range, will be far superior to the oils, referenced for use in the 1950s.

Too high a viscosity might give flow troubles if very cold and too low a viscosity may leak out too fast.

Think of engines back in the middle of the last century compared to the grades for modern engines which likely rev much more higher and the bhp/l is vastly increased.

Back in the 50/60s normal SAE30 mineral engine oil was used as 2 stroke oil, BSA Bantam Etc ! The use of Chainsaw chain lube oil on other things, be careful as it is fed into the bar groove and works through the chain, carrying the sawdust and grit etc away. It is a pumped constant feed system ! It is not intended for rotary motion and once spun out will leave journals dry, It is a specialist lube not listed for any other use including those above. ISO 32 and 68 hydraulic oils are readily available and if one considers that pumps and motors are machined to microns for rotary motion and cylinders are linear motion then these 2 specs are the ones to use on our lathes, mills Etc UNLESS a special oil or lube is secified ! There are several threads on this matter. Noel.

20/50 engine oil, or 15/50 or 15/40 or whatever is left over from the last car or bike oil change has kept my Drummmond going for over 50 years and now my Myford too. Synthetic is nice and slippery but I don't use it much so is a rare luxury.

Tellus 32 hydraulic oil is the equivalent of Esso Nuto H32 which is what Myford recommended for ML7 headstock. Readily available, if you find someone in your area who fixes agricultural or earth-moving equipment they will probably sell you a small quantity