I have had to occasionally resort to some motor oil to finish out a day out in the woods, but as some have mentioned I wouldnt make a regular habit out of it.
As far as used motor oil goes, I wouldnt do it, but I have seen firsthand a guy that used nothing but used motor oil all his life.
My uncle who ended up being like a dad to me while growing up was a first class tightwad.Used only what ever stuff the neighbor was throwing out for bar oil, and NEVER bought a new bar for his old Mac. he still has that same saw today, and still cuts his winter wood with it some 30 years later.
The same guy was quite proud of the fact that he had a toyota pickup with almost 200,000 miles on it without a single oil change. By his reasoning, a simple oil filter change was all that was necessary done every 20,000 miles.The filter by his reckoning removed all the impurities, why change the oil?
I happened to borrow that truck one day to run get parts for my truck.It wandered all over the road, and when in town I popped the hood just to check out that oil dipstick.Oil was just like mud.
But, to his credit, he never changed the oil in that truck, and it died only when a woman ran a light and T-boned him.