Another diff oil thread

[Kcalhoun27]

I used the FM from luiqimoly in the oil from LM and it didnt help much. I asked my local parts guy what was up, he emailed them and they told him it should have worked. They recommend that i flush the diff and start over with fresh oil.
So thats my plan, and then ill add the castrol for $150 and call it a day because LM clearly doesnt know what the M lsd wants and now ive hit the “buy nice or buy twice” threshold for lsd oil

[bimmer]

+1 on just buying the OEM from FCP and never worrying about it. You’ll break even on your next diff fluid change and save all this time trying to figure out the magic formula with cheaper alternatives. I’m on my 3rd batch from FCP having done it once for maintenance and now twice for my rebuilt diff (original fill and then after break in).

[CrisSilberGrau]

Can someone educate me as to the benefits of ordering from FCP vs ECS, are there certain benefits for fluids or wearable items that I'm not aware of?

[Arith2]

I used the FM from luiqimoly in the oil from LM and it didnt help much. I asked my local parts guy what was up, he emailed them and they told him it should have worked. They recommend that i flush the diff and start over with fresh oil.
So thats my plan, and then ill add the castrol for $150 and call it a day because LM clearly doesnt know what the M lsd wants and now ive hit the “buy nice or buy twice” threshold for lsd oil

They LM diff fluid comes with FM in it already. It's supposedly the right amount so you shouldn't need to add any. The only time I have any issues is in the morning when the car has been driven for over 8 hours. I'll get that groan but after a few seconds of driving, it's gone. I don't like Liquimoly but it's working as advertised for me(surprisingly). You could buy the Castrol and use a cleaned out bottle of whatever to premix so if your diff is only taking 1.4L, your mix isn't off.

[heinzboehmer]

Can someone educate me as to the benefits of ordering from FCP vs ECS, are there certain benefits for fluids or wearable items that I'm not aware of?

FCP has a lifetime replacement guarantee for everything they sell. It isn't a warranty, instead you can return whatever you want in whatever state and they'll send you a new one (even fluids). In practice it doesn't exactly work like that but yeah, basically allows you to buy something once and never pay for replacements again.

https://www.fcpeuro.com/page/lifetime-guarantee

[beefaroni]

I am a firm believer in the unicorn blood that is the BMW SAF-XJ diff oil.

I was planning on 30k mile OCI. What do you guys think the OCI should be on a car that gets tracked? Every 20 track hours?

[bimmer]

I am a firm believer in the unicorn blood that is the BMW SAF-XJ diff oil.

I was planning on 30k mile OCI. What do you guys think the OCI should be on a car that gets tracked? Every 20 track hours?

This is what Diffsonline recommends (from their FAQs) and what I plan on following with the rebuilt diff I just got from them:

"For normal street driven vehicles, we recommend changing the differential fluid every 24k and for mixed street/track vehicles, every 12k. On a dedicated track car, you will want to change the differential fluid every other engine oil change at a minimum. Ideally, every oil change is best. The differential fluid lubricates the ring and pinion gears, which transfer power from the driveshaft to the axles. The limited-slip unit requires fluid to keep all of the internal parts healthy and moving properly. Differential fluid changes areas imperative as changing the oil in the engine, and for the exact same reasons. Metal-to-metal contact wears down surfaces and creates heat from friction, which weakens parts and can lead to failure."

[macaroni86]

Radekxpl thank you so much for reposting your info from M3F! I knew I had saved it and could not remember exactly what the percentage of FM was said in that thread.

[sharadn]

See review #3 on the FCPro website.
https://www.fcpeuro.com/products/syn...1543c9#reviews

Note this review is for those with a BMW M3 E9x. The differential oil does not have the friction modifier (FM) like the BMW OEM differential oil. You will see a bunch of information by reading some of the various M3 forums. Long story short, the FM in the BMW OEM fluid is 4.6%. What that equates to is about 23ml of FM per 500ml bottle that is needed to make this equivalent to the current OEM formula. I'm not going to go into what FM you should add as there are plenty of debates, but wanted to make sure those buying it know what they need to do to make this fluid current BMW OEM like. P.S. you will still save a ton by adding the FM yourself over buying OEM. I hope this helps those buying this product!

I followed this to the T and no groaning. Matt Coyne rebuilt my diff and he put Castrol in it. I did an oil change on it after 2500 miles and followed the above guidance.BTW: I used Redline FM

[Tones]

Just going to jump in here. I just did a diff fluid change with the bmw dif oil. I only used 2 bottles though seems people are using 2.5.i only jacked up the rear to do the change is this why?

Sent from my Pixel 3 XL using Tapatalk

[911Fiddler]

Just going to jump in here. I just did a diff fluid change with the bmw dif oil. I only used 2 bottles though seems people are using 2.5.i only jacked up the rear to do the change is this why?

Sent from my Pixel 3 XL using Tapatalk

Could be. It takes 1.1 litres, I understand. If she’s not level when jacked, you’ll alter the fill level.

[Halftim3]

I just finished doing this with the car raised and leveled, and was able to get 2 and a 1/2 bottles in of OE diff fluid.

On another note, will diff fluid leak if changing the diff cover to a new cover for oe bushings while the rear end is installed/not dropping the diff?

[Tbonem3]

Yes, the diff cover, removed, will expose the internals.

Capacity is 1.2L, so 2.5 bottles is about perfect (2.4 bottles)