I generally believe that noone should use oil suppliments unless its a last resort sorta thing. Oil is carefully formulated to do its job. Adding other stuff to it can ruin this balance.
PTFE might have some value in a gearbox, but I definitely would not try using the stuff in an engine. No direct metal to metal contact should occur in an engine, or a gearbox for that matter. If that was the case, a gearbox would sieze up pretty quick. Try running a box w/o oil and see what happens! hahah
Btw Lucas Oil Stabiliser is just a thickener and shouldnt be used unless your gearbox is stuffed or something. Its been proven to cause excess foaming which is no good for lubricating gears..