I know I have nowheres near the knowledge of Rich, but I have to disagree with running Dino oil in a T56. I can see in an automatic where there are a bunch of clutches, springs, little tiny moving parts that require a set amount of friction, but a T56 is nothing like that (I have rebuilt 3 of them). All there is in a T56 is gears, synchros and bearings, basically, there are much less moving parts than you would think there would be in a 6speed. And synthetic oil, like amsoil or mobil, is designed to stick better to moving parts, granted it is thinner, but that just means that it will lubricate better. I have, and would much rather run a good synthetic in my T56 and Engine any day, automatics and rear ends are a different story, especially rears where putting synthetic wont hurt anything, but will make the diff slip more, which is good for grandma, but bad for posi.