oil_film, I posted a white paper on the board a couple months ago that reviewed adding moly and/or tungsten to engine oil. I forget the exacts and don't feel like looking it up, but I believe at the "optimum" dose rates for both FMs combined, the reduction in friction was quite impressive, somewhere on the order of about 75-80% reduction in sliding and spinning friction. However, the study stopped short of doing a mass validation to show any real world benefits; there were no extended UOAs or even long-term mileage gains tests.
Maybe JAG, MolaKule, or SonOfJoe can tell us what exactly is the intent and real-world results of adding tungsten to motor oil, since other than claiming it's superior, Ravenol and Liqui-Moly don't get very technical in what the mode of action is.