Ted Bennett wrote in message ...
What is this stuff? What makes it more penetrating than any other low
viscosity oil? Maybe some solvent/surfactant added to aid the oil's
ingress?

I'm thinking about threaded fasteners that get power-washed. Like spoke
nipples in a motorcycle wheel.

It's what resembles to me anyhow, a thin grade of kerosene. Kerosene
works almost as well, is cheaper.