I have a 1985 M635 Euro with a 5 speed manual tranny. I live in western MD and it gets quite cold in the winter. I have noticed the tranny is a bit notchy and difficult to shift when cold. What is the best gear oil to use? I would like to use the same oil year round. I have heard that Redline MTL and Brad Penn are 2 good choices. What is the best weight? Would 80W-90 GL-4 be OK?
charlson89: I called Redline customer service and they said that depending on the label on my tranny, the recommended Redline product would differ: Green label: MTL 90W Red label: ATF No label: MTL 80W90 Can you assist in determining correct choice. I was leaning toward the 70W80 in an effort to make the shifting smoother at cold temps.
I would think ATF is a mite thin... I use MTL (what's that, 75? 80? 90?), but it isn't cold here. I'd recommend MTL 80W90, but it's probably worth a phone call to the Coupe Doctor, Carl Nelson: 800 466-8184.