Some old timey service documents make reference to using mineral oil to lubricate brake parts at assembly with implication that it was the method used by GM factory.
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The 47-53 service manual has a note on brake cylinder disassembly that says "Do not use gasoline, kerosene, or any other cleaning fluid that might contain even a trace of mineral oil." which implies that mineral oil is not good.
It also says to "dip internal parts in brake fluid" on assembly.
