The factory manuals call for 75W90 ([email protected]
= 14 cSt) gear oil for the AX15 transmission, due to its design.
The Redline MT-90 or the Amsoil MTG are excellent replacement's for MTF's in these medium-duty transmisions. For extreme cold weather operation year round, the Redline MT-85 works well. Both Redline MTF's contain the same MTF additive package.
A 10W30 engine oil does not have the proper additive package as does a dedicated MTF.