synchromesh is a great product, but it is a very thin lubricant. I have heard many cases of synchromesh doing wonders for synchros and lots of damage to the bearings over time. I wouldn't recommend using just synchromesh if the tranny calls for a thicker lubricant. and yes, we do put synchromesh in subaru's at my dealership if the case calls for it. i think subaru has it's own tranny additive though. i can check for you and pm you later