"The TCP/Marvel Mystery Oil option: These are most likely about the same thing, with small changes in the recipe, so as not to infringe on another's copyright. Both are high in detergents to do the cleaning job. Neither should be used for the first time on a high time engine; about half TBO or less should be the cut-off time, for first use.
From previous link in this thread:
"Marvel Mystery oil is 30% varsol (charcoal lighter
> fluid) and 70% 30wt base oil some red dye and
> wintergreen fragrance. It is from the late 1920s."
