synchromesh here for 3 years now, I love it. Used to always grind going into 5th unless I shifted at like 2000 rpm. fixed after a couple days. can't really call it a miracle oil though because I have no idea what was in there before that, but it never grinds if you shift right.

there are a few different types of the synchromesh, search this forum to find the right part#.