One is approved by Subaru for removing old head gasket material from the gasket mating surface, and the other has a GM TSB stating not to use it for gasket removal near
Re: Old Gasket Removal and Cylinder Head Cleaning — Moped Army
How To Clean A Head Gasket Surface [Best Ways!]?
Steel Seal Head Gasket Repair | Halfords UK
how to --- BEST METHOD For Cleaning Head Gasket Surface - YouTube
How To Clean a Cylinder Head Mating Surface | Fel-Pro Gaskets