Hi guys, could any of you miata owners chime in? I'm working on my grandpas 1992 miata, and doing the transmission fluid. Ive heard the GL5 fluid doesnt like the synchros much, so I'm hunting for the GL4 stuff. Do any of you use GL5 with good results? Its really easy to find....in fact, Ive got some castrol stuff on my shelf I could use! I just dont want to cause him any problems. He's in his early 80's and just bought it!! I hope I'm like that down the road. I'm pretty happy for him, hes having a blast!