Is it ok to use the undercoating made of Boiled Linseed oil and toilet wax rings? I've seen videos…

Is it ok to use the undercoating made of Boiled Linseed oil and toilet wax rings? I've seen videos where people mix the two while hot to form a light paste and then they paint it on under their car. Would this be safe? I've heard it claimed that this is the old ZBart formula that lasts 25 years.

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