[alex2112]

Hey all, my car has 74k on it and about 5000 miles ago I replaced my car's stock 6MT tranny and diff fluids for the first time with Redline D6ATF and Redline 75w90 respectively. I did this based on recommendations from multiple sources, including this forum. At first, the tranny was much smoother than it was with the stock fluid. I was happy to have had the notchiness in the gear selector smoothed out considerably, but as of right now, I want to say the notchiness is worse than it was with the stock fluid that was in there for almost 70,000 miles. I've also found some people on here that have reported that the notchiness came back quickly after replacing the OEM fluid with aftermarket for them too.

Does anyone have any thoughts as to whether these "boutique" fluids are actually better than OEM? I don't understand how they make the shift feel smooth at first but then quickly deteriorate. I would think it should be more gradual over time than this, considering that most people recommend 30k interval changes for these fluids.

[lbernielu]

I believe Pentosin is an OEM supplier for your transmission and differential fluid - if you download their technical fluids guide you may conclude that their products are comparable to the best in the world. I had my transmission fluid replaced at 75k miles and it is still good at 114k miles.

[leebermeister]

OEM manual tranny fluid is good stuff, but definately not "life time". My 06 tranny has the LT2 sticker. I ran D4 for about 10,000 and didnt like it at operating temp. Switched out with Pentosin LT2 and its much better. You 07 is probably LT3, so make sure you put the correct fluid in.

[alex2112]

Thanks guys, I'll look into the Pentosin fluids. I'm really not impressed by the Redline, especially in the tranny.

[JoosyJoos]

I'm pretty happy with Redline in both my e36 and 335i. I plan to replace the Redline in my diff and transmission every 30K miles in the 335i. I haven't noticed any "notichiness" w/ the 15K I've put on my car since I swapped it the first time.

[Meeni]

The redline fluid is known to cause issues on BMW MOTORCYCLE crown bearing (in the "differential" -so to speak- of the MC). It works fine in the transmission on these bikes (it actually smoothes the gear shifting).

I do not know of any issues on our cars, and I have also heard great reviews.
However, considering that 1) Redline and other threndy brands have not filed to receive the API specification (these are quality products, but not running the correct API is always a risk, as the MC crown bearing story illustrates), and 2) the OEM fluid works well, is rated for the job, and is often cheaper than alternatives, it may just be simpler to stay with it.

[AlanAZ]

Turner Motorsport put RL ATF D4 into my E46 MT, and it worked well, especially during the cold Boston winters, for several years. I have the same D4 in my E90, and while it worked brilliantly the last hot Phoenix summer, it feels like able to easily crash the gears this summer -- so it's not lasting well, and I may go back to OEM.

I was emailing with Mike Miller, and he's recommending RL MTL, but everything else I'm reading suggests it will be stiffer than OEM during cold winters. Given my winters are mild, it may be worth putting up with some notichness for a few months, and better for the many summer months..

Anyone mixing the two?

http://www.bimmerfest.com/forums/sho....php?p=6088492

Another interesting thread:

http://www.n54tech.com/forums/showthread.php?t=7264

I will continue to use RL 75W90 in my diff. every 50,000 mls, next change at 100K.