I just read Bob Helt's article in the CORSA Communique (Gear Lube Selection). He mentioned that GL-5 may or may not have the anti corrosion specs necessary for our old synchomesh grinder boxes. Anyone know for sure that GL-5 is OK or should I take my Castrol Syntec synthetic gear oil back to NAPA? It also meets the requirements for Mack GO-H/S. What does that mean? thanx! Merv Krull Salmon Arm