Doesn't say, but I have never used anything but the thin washer type gasket and never had leaks. Only real leak I had trouble with was the big aluminum plug on my Quickfuel pressure regulator. It stripped out the first few threads on the plug, but I got it to seal up, albeit I had to tighten it more than I wanted to.
You'll eventually crack a thin cast aluminum oil pan, or transmission housing. The Teflon tape effectively increases the diameter of the pipe thread enough to crack stuff. I have often seen written warnings against using it on parts like this. Anyways, the liquid brush-on sealants are usually easier to work with anyways.
--agree w/ the above! ---------- if your cracking anything, your the fault , not Teflon tape. been using it off and on for around 47 yrs. my favorite is pure permatex Teflon paste. sticky and gooey, stiff when cold or old, but good stuff. just don`t over do it .
