What kind of gear lubricant are you guys using in the WRX 5MT? Any problems? Can you shift into first without grinding(assuming you didn't have any problems on the original oil). What weight is the oil you are using?

 

i am using royal purple synthetic in in my transmission but they're dog gears but i haven't had any problems shifting or anything
not sure on the weight though

 

I tried using Mobile1 GL-5 75/90 with terrible results. First gear would grind and bounce back at any speed above 5mph going into first. The rest of the gears didn't feel very reassuring with higher RPMS shifts.

I drained and put dyno GL-5 75/90 back in but it's still grinding thanks to the nice $40.00 coat of Mobile1 on everything in the gear box. It is much better this morning but I'm going to run it for a few hundred mile and flush it out with another fresh dose 75/90 dyno and hopfully return to normal opertion.

 

Did I mention that this really sucks?