MT-90 meant to be a very good oil, many people recommended me on mr2.com
However, it didn't improve my shifting what so ever. I had worn synchros and I've been told this oil very much likely smooths up my shifting. Well, it didn't.
Maybe my synchros were that bad, I don't know.
Brought up my box to Elmhall gearboxes a month ago and when I said what's in it they said MT90 is too thick. After they repaired my box (2nd 3rd synchro change),they recommended me to put in 5w30 fully synth
http://www.edsportrallysupplies.ie/RaceOils.htm