^^^^ That's the other downside to not using a motor oil in the motor... There are several flavors of acid inhibitors in motor oils.
I believe he was referring to the oil based stuff used in hydraulic cylinders to angle snowplows and the three point lift on my tractor.
Brake fluid is generally a glycol based lightweight hydraulic fluid that has more in common with anti-freeze than lube oil. It is a hydraulic fluid but based on his comment not what he was referencing.
There are some really light oils with a heavy detergent package that are specifically designed to de-sludge and dislodge crud. I wouldn't use them either. That crud has to go somewhere and Murphy tells me he will make sure it gums up something far worse than it was gumming before.
#10 UTF or Dexron III might do the same thing.
Would #10 UTF Hydraulic oil or Dexron III get you home for a real oil change when you discover you're a 2 quarts low in East Betty BooFoo at midnight? Yes.
Would I run it for more than a short time? NO.