I have ten gallons of used motor oil and never thought of using some of it to start the brush on fire.
It is a great way to get rid of waste oil and it burns very hot. Some will have a conscience about using it, but I think that a hot, clean burning fire is preferable to a smoldering failure of a fire. I have a neighbor across the road that likes to fill the area with smoke from wet leaves and brush and what smells like burning garbage. Hot fires don’t make much smoke.