Pat...Redline MT 90 is for the hypoid style ring & pinions we use in the
Vanagons
MTL is more for the Jetta style tranny's
MT90 is a bit heavier than the MTL , but both seem to work about the same
in the real world as you can expect easier shifting than other synthetic
gear oils. I can tell the difference on the inside of the tranny when
redline or a similar  oil has been used.
Change even the good stuff every 30K miles for longer bearing life.

Daryl of AA Transaxle