I always have a good bit of used motor oil, hydraulic oil sometimes, and even occasional transmission fluid. It's very difficult to find places to recycle it in these parts, but I have two ways to get rid of it that I think are reasonable and not too environmentally damaging, IMHO. I do a good bit of prescribed burning, for hardwood control in the understory of pine stands, hazard reduction in cleaner pine plantations and also site preparation burning where large piles of tops and logging debris around decks must be disposed of before planting. I mix about one half used oil with gas for drip torch fuel instead of having to buy diesel to mix with the gas. This only works well with the Panama brand torches since the Sure Seal or Seat Tite brands don't seem to stay lit with the motor oil. I also pour some on the top of brush piles, letting in soak in for a few minutes to help in igniting the brush and to get rid of the oil. I don't pour enough out for it to run off onto the ground. I can easily get rid of twenty or thirty gallons in a day by doing this. I believe that the brush piles generate enough heat to pretty well incinerate any oil and whatever it contains. YMMV.