DIY OEM Diff fluid

Just wanted to share what I did to replace my differential fluid a couple of weeks ago. I ended up buying some Castrol Syntrax 75W140 and Ford Friction Modifier and mixing the two. I got the idea from this thread on M3Forum. The good information starts around page 2 or page 3.



I got the Syntrax from ECS. It's for Mercedes Benz, but is the same fluid BMW uses (without FM).







I got the Ford Sturaco friction modifier from Summit Racing.









HOW TO:



I bought 3 bottles of Syntrax and 1 bottle of Friction modifier. I measured down 0.75 inches from the level in the Ford friction modifier bottle and added that to each of the Castrol bottles. You will have some friction modifier left over at the end. I used this post from M3f for guidance. Be sure to shake up the bottles before putting them in the diff. I had to use a fluid pump to get the stuff in there.



I used about 1.3 liters of fluid to change out in my diff. That ended up being about the same amount that initially came out.



Don't forget to buy drain/fill plugs (one of each).



Anyways, I couldn't justify spending $150 on OEM diff fluid when I could make this for around $50.



Car has been fine for the last couple of weeks. I did not have any groans/noises from my diff in the first place, and I still don't have any.