Used motor oil gets drizzled onto the barn cleaner chain to keep it quiet and not so rusty. Even though we don't have cattle any more (for now...), it's still handy to clean up my workshop/barn floor by just sweeping into the drop, and run it out into a waiting pickup bed for disposal.
As far as cheap oil, around here it's TSC all the way. It's a little thick in the winter, but I just warm it up on the dash of my truck when cutting, and it flows into the crankcase well enough. I would love to be able to buy a 5 gallon bucket of bar oil though. It would probably last me a year, and I would have another 5 gallon pail for using around the farm when it was empty.