I ran a mix of Redline MTL90 and MTL it in my AX15. I went with the mix because it does get well below freezing here at times and the AX15 is known for cold shifting issues. Serious improvment over cheap stuff.
When I rebuilt the tranny (bad synchros when I got it) I put in GL4 from NAPA with the intention of draining and refilling with synthetic after a week of breakin. It shifted so bad with the cheap oil that I thought I screwed up the rebuild and was ready to tear it apart again. I decided to change to the Redline first and see what happened. All the shifting problems disappeared immediately and it shifted great. The first couple of 1-2 shifts were still a little stiff on those -15*F mornings though. :}