I think it will have more to do with the machine that the grade of oil.
Differences between 32 and 68 as far as lubrication will be negligible, if it could even be measured.
Where it matters is size of the machine, does it live in a cold workshop for the winter months and questions such as this. The reason being 68 is a fair bit thicker and has more drag at low temperatures.
Used to have a Harrison 140 running on 20W motor oil [ everything ran on 20W motor oil seeing as he had a 900 gallon tank of it for the trucks ] and it wouldn't run the top two speed without a good 15 minute warm up at lower speeds and then it was fine.