Redline 75w90 or 75w90NS for a BMW rear diff?

[Quattro Pete]

Assuming the rear diff has no limited slip (like in my 530i), would the Redline 75w90NS be preferred over the regular 75w90? Which Redline are you BMW owners using?

FYI, the OEM fluid is Castrol SAF-XO 75w90, I believe.

 

[Lonnie]

Talk to Dave at Red Line for Red Line's answer to your question.

 

[unDummy]

Its a coin toss.
For manual transmissions, I'll also recommend the NS.
For open 'ends and x-cases, it doesn't make a difference.
For LSD equipped vehicles, always use an additive.

 

[Craig in Canada]

In my 1998 E39 I use the standard 75W90 which is also what Redline recommends. From the product description, however, you'd think 75W90NS would be the same or better.

75W90 is easier to find, and would work fine, IMO.

Although it doesn't apply to any BMW I know of, GL-5 lubes including 75W90 and 75W90NS should be avoided due to soft metal compatibility and other reasons. The LSD adds in the standard 75W90 will not play well with the synchros. If you need 75W90 weight in a manual, use MT90.

FWIW, they recommend D4ATF in my E39 ZF 5-speed for easiest shifting. I'm using MTL for a slightly higher viscosity (long-term protection and closer match to factory fluid) as well as to use a fluid actually designed for synchros. In the winter it's a touch notchy before warmed up, in the summer I can't feel any downside.

Craig.

 

[Quattro Pete]

Thanks.

I'm only considering the Redline for the rear diff. For the manual transmission, I already picked up some RP Synchromax.

 

[Craig in Canada]

Whoa, I forgot a word or two in my post and edit time has expired.

My GL-5 comments were specifically about manual transmission use, not diff. (QPete already understood this)

RP Synchromax is OK, and constantly talked about in Bimmer circles. I didn't think it was anything special, didn't improve shifting for me any more than a fresh change with anything, and was very thin. I went back to Redline products. "Better" shifting (which wasn't any better for me) at the probable expense of longevity isn't my cup of tea. I think the V8 guys with the 6-speed Getrags seem to get more benefit out of RP than the 5-speed ZFs that we have.

Craig.

 

[Jim 5]

I am using the redline 75w-90 in my 330ci diff. FWIW, it seems to be the lube of choice on e46fanatics.com.

 

[Quattro Pete]

Quote:

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Talk to Dave at Red Line for Red Line's answer to your question.

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I emailed them my request 2 days ago. Still no response...

 

[sprintman]

2000 Outback. From memory (could be wrong) 75W90 in the rear diff and 75W90NS in the trans. Syncros need to get hold of an oil hence you don't want the slippery additive in the g'box. Just followed Dave Granquists instructions to the letter as he knows his stuff. Subaru dealer head mechanic didn't believe the Redline had done 60,000kms in g'box and diff when he changed it a month back. He said somebody had recently changed both oils as they looked like they did when filled. Can't get a better product recommendation than that. Less wear, better shifting. Redline gear oils rock!

 

[Thatwouldbegreat]

I keep at least a case of each Redline product in stock.

75W-90 for diffs, 75W-90NS for Subaru Transaxles, MT-90 and MTL for manual transmissions, and D4 ATF for automatic transmissions and power steering.

Usually MT-90 goes in German cars' gearboxes and MTL in Honda geaboxes.

I've never tried emailing Dave, but I've reached him by phone almost every time I've caled him. Great guy providing top notch technical support.

 

[Jim 5]

I have heard many recommendations for the D4 ATF in BMW manual gear boxes. Especially in colder climates. I THINK they recommend MT-90 for hotter climates like yours...

 

[Quattro Pete]

OK... finally got a response from Dave. As others here suggested, he recommends the 75w-90 for my rear diff.

 

[khunjeng]

for a high powered app i.e. double std output...would it be better to go the 75W140 instead on the 90? I think it would but the low temp visc is a bit high.