Well im going to add my .02.I have been a plumber for 15 years now and this is what I tell everyone.If you don`t want a leak on any threaded connection use teflon tape and dope togeather.If it is in an area that you dont want contamination put the tape and dope on a couple threads back.Use regular ol teflon tape but the secret is in the dope.Use a non hardening type like rector seal #5 or gasoila.If you use a harding type like leaklock or expando it will leak if there is any vibration, movement or thermal expansion.Anyone here can tell me im wrong but I use this every day at work and I can tell you this,it will hold at least 200 psi on a threaded connection.BTW put the tape on first than the dope..Hope this helps someone out.
