Well, for you used oil for bar oil fans, my dad was one of those. He died of liver cancer at age 66. He never smoked either.
Used bar oil is not good for you, it is not good for your bar, it is not good for your oil pump, or for your saw, and it is not good for your chains. It is not good for anything, really. But go ahead and keep using it on your property, breathing it in and in your saws and getting all over yourselves and the environment that you live in. And good luck in the long run. Heavy metals and toxins from blowby gasses build up in your system over the long run. And your kids and your pets. And pretty much any other living things around y'all.
Me, I use soybean oil (labeled vegetable oil) in my saws. For you cheap ass people here, its all of $5 for a whole gallon at Wally world. While not as 'cheap' as "free" used engine oil, it is 1,000 times less toxic. Yes, one thousand times less toxic. No tacky stuff is in it, but you do not need it. Just crank up the oil pump in your saws and spray away. It will degrade naturally. If you spill it and the dog laps it up? No problem. If you get it on your clothes and the wife gets it on her hands doing the wash? No problem. Hell, you can drink the stuff. As for wear, I have seen next to none running soy oil on my bars and chains for the past 6 or 7 years now. The only issue is that the chains can become sticky after a few months of no use, and that takes dragging the chain in a log for a few seconds to get it rolling again, and that is the only downside I have seen. Did I mention the price? $5 a gallon.
But carry on using one of the absolute worst products I can think of in your saws. Short of leaded gas. For what, to save a few dollars? Just do not cut on my woodland property.