AchtungE60

This is a waste of time and money. Once I changed differential fluid on one of my M/T BMWs with about 124K miles on it. had the fluid tested afterward and I could have used it for another 124K miles easy. I agree with BMW it is lifetime fluid. ONly on this one.

Stumpel

I tend to agree with you on this one. While you cannot tell much from appearance, the old fluid looked very clean.

Stephen Max

I'm with Achtung on this one, too. I have owned over 16 cars in over 40 years of driving, most of them driven well past 200k miles, never ever changed diff fluid in any of them and have had zero diff problems.

squidzilla

The problem with me leaving it in there forever is I only drive about 5k miles per year. At the rate I am going my 2004 will hit a 100k miles in 7 years or so. That is in 2019. Given the 85.00 cost I paid my indie, I felt it was a small price to pay to avoid having what will then be 15 year old differential oil in my car.

kskane

I beg to differ with Achtung and ANYONE who believe's BMW's lifelong oil theory. I did the differential oil change on my '04 E60 at 130K's and the I don't think the previous owner ever changed the diff oil, so after 130K's the oil was BLACK full of contamination which should have been change along with transmission oil. So IMHO, if you really want to care about our vehicles on long run, change the lifelong BMW oil contrary to BMW's publications, as it it meant to be lifelong only for the period of warranty, not the life of vehicle. If you don't agree with me after looking at the pic, then I guess good luck to you and your vehicle.

BimmerFan52

I would agree with Achtung and Stephen Max that most people never address the rear differential fluid and never experience a rear differential failure. The rear differential is a fairly robust and yet simple set of gears in a sealed system.

But most people also never address the ATF, brake fluid, power steering fluid or coolant and the vast majority never have problems with transmission, brakes, steering or radiators either.

Dirty rear differential fluid or even low fluid level is unlikely to cause failure of the rear differential, as long as the gear oil is of minimal quality (and certainly the BMW OE fill meets that). However, both conditions can lead to noise and/or vibration of the rear differential over time.

If changing the fluid was a six hour job requiring special tools and standing on one’s head then I also would probably avoid it. But an inexpensive and simple one hour job to insure the fluid is fresh and fully filled to help prevent noise and vibration? In my book it’s a no-brainer. But that’s what makes reading this forum interesting. Each of us determines where spending our time and money is important. Cuique suum – To each his own.

beaker

If you want to believe in lifetime fluid, feel free, but I don't. I change the oil in my rear diff every 30K - 40K. I did it a few weeks ago and used regular XO fluid that I bought from the dealer; before that I used Red Line 75W-90. I had the Red Line tested - here's the info from Blackstone:

"Iron is certainly the dominant metal in this sample from your differential. Universal averages show typical wear levels for a BMW differential after about 28,400 miles on the oil. Iron might be a little on the high side, but not enough to call a problem after just one sample. Iron is from the steel parts and chrome is likely an alloy in the steel. We run a TAN (total acid number) on diff fluids and that was 4.0 showing some acidity. Try 30,000 miles on the next fluid and check back."

Unless you have your oil tested, any decisions are based on hope and theory - not facts. I like to base my decisions on facts.

AchtungE60

I never said I agree with BMW's lifetime fill for all fluids. But do a cost/benefit and perhaps you'll come to my conclusion. I'll stick with my experience and ownership of only BMW over the last 12 years. Gave my E39 to my cousin and it has over 400K+ mi. on the clock and never changed the differential fluid. I changed my 99' E46 because I had a different mind-frame back then but it's a complete waste. I won't repair something that doesn't NEED it. The Color doesn't tell you anything about the differential oil. I drive the E60 but I won't poor my life or energy into a car anymore. A car is a car and they're all made up of the same parts.
The pic you posted can be of anything, doesn't mean it's your hand, your oil, your grime, etc etc but thanks for the pic.

baveagle

Doing the diff. fluid change today. Car is at 35K miles and doing it is easy and low cost. Following Mike Miller's (Tech Editor of Roundel) recommendation.