LOL...I have done that, also painted fence with used motor oil. I used to get extra from a dealer who did oil changes...
Learned this from a farmer Father-In-Law...
It definetly works. Preservative and repells bugs in the ground.
In the Adirondack Mountains (probably elsewhere) it use to be common to stain board and batten or other wood cabins with gasoline. 1/4 to 1/3 the cost of commercial stain, of coarse you have to be very careful in the process, until it dried. Slightly darker aged look with character immediately.