[aerohead]

I presume that you already have a full-synthetic lube package.
Whatever Subaru recommends, rating wise, you ought to maintain.
Years ago, I attached a half-dozen baby food jars with different lubes to a board and placed it in the freezer overnight.
Next day, I uncapped all the jars and tipped the array over a pan.
Regardless of 'cost' and rated viscosity, they all 'poured' identically, from the most expensive racing lube, to the lowliest, entry-level lube.
I'm uncertain as to whether there's any low-hanging fruit available to us, gear lube wise.