Chris, Erich, and Sslater thanks for the input. For the sake of discussion, please allow me to dwell on the subject!

Several reasons were stated for the use of grease on the R9/s:
1.
Oil runs dry pretty quickly - I agree but only if one allows the gun to sit long enough w/o regular cleaning. Maybe most people don't clean their guns often hence the recommendation from the factory. But if this is the only reason, then ALL guns should also use grease as lubricant. Does anyone here use grease on all their guns? On another note mentioned, the newly synthetic stuffs are truly amazing for prolonging the oil’s evaporation.
2.
The R9/s is a shoot-little-carry-a-lot-gun - Same as above: if you don't plan on cleaning it regularly. The R9/s is also a tightly tolerance gun hence oil should be more desirable for best performance.
3.
Dissimilar use metals – Could be! Could be! :-/
In short, I wholeheartedly agree that
persistence of constant lubrication is the key. But again, this logic should apply to ALL guns and not just to the R9/s.
Chris: I use nothing but synthetic stuff these days, specifically the Militec-1. Along with their oil, I also use their grease. As stated in other thread, I like their stuff very much. If you get it on your skin, washing it off doesn’t seem to go away quickly! If feels extremely slippery over the Mobil-1 of SuperLube stuff that seemed to wash off faster!
Cheers!
