turboawd - excellent post, thanks.

Like rctmthouse I also have a slightly wet transmission sump but no evidence of where it is coming from...however the oil is definitely clean Shell ATF 1375.4 (ZF Lifeguard 6) as shown above which is very helpful. It's clean because I had the gearbox oil and sump changed recently...

 

At what mileage would you guys think is optimal to even bother changing the transmission fluid and yikes that oil sure was black.

 

Depends on how you drive and what size engine you have, for me 70k miles was about right. My old oil was quite dirty but not black.

 

I guess i better change the fluid in my e90 since i just hit 80k. I always thought it was strange when the SA told me it never gets changed like its some magical fluid in their transmissions. Thanks for the post turboawd!

 

Im still on the fence abt it but everyone that has done it only states good results

 

Notice in the other thread you stated your car has 120k miles, I would definitely do it unless you really believe the lifetime fluid theory from BMW. It was a good learning experience for me. Was not into fixing my own car before owning the E60 but since I own it, it's like a got the DIY bug. Scary but the satisfaction afterward is worth it.

 

All Data Chemical Sheets with Viscosities and flash points etc:

 

am i reading that right, the pentosin atf1 has less viscocity than the zf fluid?

 

Yes

 

i'm not liking that. i'd go with mercon sp or even castrol before using the pentosin. the pentosin seemed the most different of the fluid i had listed.