Engine oil

Ran across an old towmotor forklift close to 50 years old. We have it a couple months use it around the shop it works pretty well. I'm going to change your engine oil and I did not know what the previous owner used. And something that old is it fairly critical to use non detergent motor oil. It also raises the question would SAE 30 be too thick for the winter. I did not find much an operator's manuals online.

Engine oil