I think I asked this and never got an answer. Myabe nobody knows but that sure would suprise me from this group. I want to replace 6 speed and rear end oil with synthetic!!! I understand that MOPAR is big $$$$'s. Since Mopar does not drill for oil, I don't think, does anyone know what brand they use with the MOPAR label? Otherwise I suppose AMSOIL is the ticket for both with no friction modifier in rearend. I will be towing and feel synthetic is the way to go specially here in Arizona!!!