Kinda like the title says, which fluid do you recommend I use in my GSR transmission? I'v used royal purple 5w30 motor oil in my friends d16 and in another friends k20 and they both were smooth as butter. However i'v been reading about royal purple synchromax and GM synchromax. Should I go with the Motor oil which is recommended for Honda or will the synchromax be a better choice? Thanks.