Am Samstag, 26. März 2016 19:34:54 UTC+1 schrieb Ignoramus20764:

Hydraulic oil lasts about a year. Used hydraulic oil is nice and
clear, not like black used motor oil. Hydraulic oil also clings better
and has anti-rust additives that are added to resist internal
hydraulic corrosion.

I also did this with hydraulic oil in the fire extinguisher. I'd say my coating lasted about two years in rain and sunlight, but it was on equipment that wasn't moving.