Tranny / differential fluids - when to change?

[nicknaz]

Originally Posted by jparnes1

Nick, FWIW, Mike Miller requests that his maintenance schedule not be posted on the internet. It's copyrighted and periodically updated.

Tranquilty, Blackstone will test any oil in your car. The report is technical but their results and recommendation are written clearly.

Thanks for the heads up. I edited my post.

Pretty funny that recommendations copied from an old BMW maintenance schedule are copyrighted...

Tranquility, look at the blackstone report explanation link for diesel/gas... it says in plain english at the end of the comments " We think you could run the oil a little longer, if you're interested" (not sure how much more straightforward it can be!)

http://www.blackstone-labs.com/report-explanation.php

I think jparnes and I have both said it like 10 times now... you will not know if the oil change intervals you are using are "correct" without analyzing the oil...

Are you looking for a direct answer as to whether the gearbox and differential oil has been in your car too long (72k miles) ? Yes, I absolutely think so. I would absolutely have changed those at 30k miles if the car was a keeper.

Another point of view on gear oil service is from this Porsche document, which on page 3 shows a recommended gearbox oil change at 90k kms

http://www.porsche.com/filestore.asp...letype=default

[jparnes1]

Interesting on that Porsche doc...180K km (112K miles) MT oil change frequency. Yikes!

[nicknaz]

Originally Posted by jparnes1

Interesting on that Porsche doc...180K km (112K miles) MT oil change frequency. Yikes!

That is all customer paid service too, so it is not like Porsche is saving any money from the longer change intervals.

Maybe the new gear oil tech is just a lot better these days (in the same way that 3k mil engine oil change is now too short given advances in engine oil tech).

I wondered why the PDK internal was 1/2. Maybe it is because the clutches are in the oil? By that thinking, maybe the old school maintenance interval for DCT gear oil is 15k, like ATF change interval, instead of 30k, like the manual transmission interval

Other interesting line item was "service convertible top" every 30k km/ 2 years.

Given all the posts about the E89 top, that could be a good one to add to "old school" maintenance for E89 specifically

[jparnes1]

Originally Posted by nicknaz

That is all customer paid service too, so it is not like Porsche is saving any money from the longer change intervals.

Maybe the new gear oil tech is just a lot better these days (in the same way that 3k mil engine oil change is now too short given advances in engine oil tech).

I wondered why the PDK internal was 1/2. Maybe it is because the clutches are in the oil? By that thinking, maybe the old school maintenance interval for DCT gear oil is 15k, like ATF change interval, instead of 30k, like the manual transmission interval

Other interesting line item was "service convertible top" every 30k km/ 2 years.

Given all the posts about the E89 top, that could be a good one to add to "old school" maintenance for E89 specifically

It could be the convertible service relates to the soft top material - cleaning and preserving.
This whole maintenance interval thing is fairly subjective. I used to change my engine oil (Redline 5W-30) every 10K when BMW said to change every 15K, but then they increased the frequency to 10K (for later MY turbo cars), so I'm changing at 7500. Blackstone said my oil was OK at 10K, but BMW's switch spooked me. As I said, subjective.

[nicknaz]

Originally Posted by jparnes1

This whole maintenance interval thing is fairly subjective. I used to change my engine oil (Redline 5W-30) every 10K when BMW said to change every 15K, but then they increased the frequency to 10K (for later MY turbo cars), so I'm changing at 7500. Blackstone said my oil was OK at 10K, but BMW's switch spooked me. As I said, subjective.

Haha. subjective is a very politically correct way to put it.

It takes a very OCD car-nerd (like me) to go through used oil analysis etc. and I think that same OCD can make owners feel the need to "exceed" the manufacturer recommendations regardless

My speculation is that BMW changed the mileage of the oil change from 15k to 10k because too many owners did not know the cars need to be brought in for an annual low mileage oil change. On a 10k miles per year leased car this could lead to some owners not doing an oil change for 1.5-2 years

As your used oil analysis showed, 10k miles was fine for the oil, so 15k miles might actually be credible. In hindsight, I should have taken a sample of my car's oil after its annual 12k miles oil change to share with the group)

[tranquility]

Thx for the additional comments. Is Blackstone the best one (only one?) that does analysis? Any other viable alternatives?

I'm gonna get their free kit and have my engine/tranny/diff oils tested later on.

[nicknaz]

Originally Posted by tranquility

Thx for the additional comments. Is Blackstone the best one (only one?) that does analysis? Any other viable alternatives?

I'm gonna get their free kit and have my engine/tranny/diff oils tested later on.

I haven't look into it in a few years but back then they had the clearest reports so I chose to use them

You could look at bobistheoilguy.com

There is a HUGE community of people who are really, really into oil and that would have some leads on alternatives, if any exist