Originally Posted By: 92saturnsl2
Originally Posted By: unDummy
I haven't found a GL5 that WASN'T yellow metal friendly with regular 30k intervals in a normal environment.
That attribute of GL5 is real and can destroy transmissions even in short period of time. Different transmissions have varying amount of those metals, but the use of GL-5 will cause wear regardless.
There is a reason the vehicle manufacturer recommend GL-4 for manual transmissions, which most do. If you want your vehicle to last 200k, put the right fluid in. You're playing the lottery when you use GL-5; Odds are against you that the GL-5 will cause premature failure-- Often much sooner than you'd think.
Just relaying my experience with GL-5 gear oils and I agree that if GL-4 is specified, it is wise to use it. I drove our 1994 Nissan Altima SE on Mobil 1 75W-90 LS (GL-5) after ~20K miles until 200K miles when it was totaled. Mobil 1 GL-5 used every 20 to 25K miles. I drove our 1998 BMW Z3 2.8 on Mobil 1 75-90 in the tranny for 30 to 35K miles. No issues, however switched to Pentosin MTF2 75W-80 GL-4 on the Z3 a few years ago. Also use this on our 328Ci. Running GL-5 non-synthetic in the Brat (front and back). However, the Brat specifies GL-5.