Has anybody run Amsoil 80/90 synthetic gear lube in their blower? It is GL5 rated. Or just traditional 85/90 dino gear lube?

I've always used the Merc High Performance GL...Griff ?

I used the same. I used it in my drives as well so no need to buy something special. It worked fine for me. Almost 500hrs on the 177 supercharger without ever being apart. Changed it with every oil change about every 25-30 hrs or so.

That is what I always used also.
Eddie