AtlasE61TT

So I'm in the process of changing both the front and the rear differential fluids, and seeing what is the best option. With some research it seems like the top picks are oem, redline, and amsoil. I don't have any experience with this so I'm trying to gauge my choice off of what other e61 owners have experienced. Are there any advantages to using anyone or the other when it comes to diff fluid? And does become modded compared to oem have any effect on the brand of oil you should use?

seanjordan20

No real advantage. Those are some good oils and either will do. My last fill I used Red Line on because I could get it the fastest. These fluids last no matter which one. I had the original fluid in until recently 190k miles on it. The fluid didn't look bad at all. A modded car plays no part in it unless you are pushing some serious extra HP then you would want to change it more frequently. You're not getting much HP out of an i6 E61

AtlasE61TT

that's good to know , wasn't to sure about how the hp would affect the oil overall. I'm at about 150k and I'm pretty sure neither the back or front diffs have been serviced ( only owned the e61 for a little over a year now). Im just doing all the maintenance items and weak points on the car before i get into adding some real horse power. Appreciate it

AtlasE61TT

Do any body know which one of these would be for a 2009 e61 535i xdrive? Or how to trll if you have the 188lw or the 215lw rear axle?

seanjordan20

You're getting too technical. All you needed to know was if it was limited slip or not which BMWs aren't. 75w90 is what you need if not getting BMW fluid. Ensure it's not limited slip fluid. 2qts

Porch

Red line has all the recommendations on their website, and are super helpful by phone or email. But front/rear diffs take gl5 75w90, transmission takes d6 atf, transfer case takes mt-lv. All red line products.