Dont use old engine oil, all you trying to save a penny....... your not!
It's just you dont know enough so do some research educate yourself, then use bar oil that is made for the job. Ok, any pil is better than none but come on, you spend a lot of money on a saw, bars and chains so why not use the best oil you can and have the machine running as it should. Sorry if this hurts a few but it gets to me when I see and read how much some really dont know and should not be let loose near a saw. Rant over now you can kill me