I picked up a 1999 Corolla about a month ago and lately the shifting has been a bit rough during cool mornings until the car warms up. I'm thinking about changing the transmission oil since I don't know when it was last done. I've been doing a bit of research and heard some good things about Red Line MT-90 and was wondering if anyone has had experience with it, or if another oil is recommended. From what I've been reading it seems even though 8th gen Corollas can use GL-5 it seems to respond beter to GL-4. Also would I run into problems with gaskets and whatnot using synthetic oil like I could possibly encounter using a synthetic engine oil?