Its simply a little more barrier on parts versus oil alone !!
* I run 3 of them in my 7.3L P.Stroke per oil change
16 qts and anything I own with an oil pump
They have helped keep my jewels rolling on.
Anyone that has torn down an engine that used STP consistently knows the stuff has a thick film that sticks to everything. I think one big advantage for using it is reducing dry start wear on a car that sits for extended periods between start ups.