The young chap at Bavarian Autosports told Me that yes, red line gear oil is used in the Diff for my final drive of 325ix (1990) can anyone Verify this before I do something dumb.
thats what everyone uses. rogue engineering uses it, turner motorsports, most of e46fanatics.com apparently the stuff works well, ive even seen claims of it quieting a noisy diff.
Red line stuff is good, attested by the number of folks who believe in it so strongly. Royal Purple is another one along those lines....and my personal choice. But I have a thing for MoSO4 (Molybdenum Disulfide) due to personal experience across several different subjects. Byron