It was my own fault! I collected about 100 litres from a nursing home last week. One drum was marked Shell Tellus, which from my days working on ships, I knew was mineral oil. My train of thought was how the hell did a nursing home get hold of an empty Tellus drum, never mind the oil looks nice and clean. It was only after I'd started pumping it into my settling barrel did I notice the different smell. I've now got 35 litres of hydraulic oil / veg oil mix to deal with.
I therefore claim Muppet of the Month award!
It does, however, beg the question ... what the hell does a nursing home do with hydraulic oil?