Here are some quotes from my forestry forum...
"NEVER use motor oil, it will burn up your bar and chain way too soon to be cost effective. Used motor oil will sling off twice as fast because it is all ready broke down, and since it's flying off the chainsaw asap it will all end up on your boots and pants making a big mess." - RECYCLE1
"Yes, bar oil has an additive that is extremely sticky, that keeps the oil sticking to the bar groove and chain. I actually have a quart of the stuff and it is amazing. I got it from an oil distributor and I think it's called Mac T or something similar." - TREEMAN2
Back to the Chainsaw FAQ.