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This thread has really grown by leaps and bounds, fortunately however, buried within it is some really great information. One of the best posts, if not THE best IMHO, is #180 above by Weasel. I agree with basically everything he is saying, but at the same time I want to throw in a few of my own comments / observations into the mix.
1. BMW recommends 100,000 mile transmission fluid changes, not "lifetime" which actually is a recommendation for other other fluids such as coolant. (Now let's forget for a minute what is the motivation behind this recommendation) The caveat is that this recommendation applies to transmissions that were operated under "normal conditions." What constitutes "normal" I personally have no idea. Is it me driving a car or my grandmother? Further, in the case of a vehicle specifically designed to go off road, tow up to 6,000 lbs, and yet still perform like a sports car, I REALLY have no idea what is "normal!" In any case, the recommended fluid change interval is in fact different for an X5 driven in not-normal conditions (let's put it that way).
2. The multitude of problems that come with trying to define normal / not-normal situations are pretty obvious. So here's just one example. If you bought your car used, who knows how the previous person drove it? Maybe they pulled a trailer every day up until the point of sale? Maybe they thought they were Michael Schumacher (though not the current dude in F1)? Or maybe they drove to Bergdorf's every other day for shopping? All 3 of which I would consider not-normal, for differing reasons. Since you don't know for certain, perhaps an early fluid change is the way to go? And since you really DON'T know, perhaps an early fluid change at ANY mileage is the way to go?
3. In something I read, ZF seems to back point #2, however they state that looking at the fluid should be your guide. Last time I checked, my eyeball did not contain a microscope and built-in fluid analysis equipment to make an educated determination on fluid composition. Few people have JCL's experience in this stuff and so unless the fluid is burnt to a crisp, I don't know any one of us normal people who would know if indeed the fluid needed changing or not without some sort of detailed lab report to go by. Interestingly ZF recommends that the fluid be changed when it smells burned, however "the damage is already done." Nice one.
4. On their website, (see attached screen shot photo) they discuss their LifeGuard Fluid 6 (which is a special fluid blended by Shell for ZF; Shell calls it M1375.4; see photos) as offering extended maintenance intervals to 100,000 km / 62,000 miles. Interesting. This is certainly no 100,000 miles / 162,000 km recommendation. So if an EXTENDED maintenance interval on this fluid (which is after all the OE fluid and the ONLY fluid recommended for this gearbox) is 62,000 miles then perhaps driving in not-normal circumstances would warrant fluid changes at intervals shorter than 62,000 miles?
5. The transmission maintenance recommendations from ZF (see attached fluid recommendations and interval recommendations below) have some different information. Here they indicate that should not-normal (my words) conditions exist, maintenance intervals should be as low as 80,000 km (49,600 miles) or as high as 120,000 km (74,400 miles) or 8 years. So now what does this mean? If you don't have a clue how your transmission was treated should you have the fluid changed at 49,600 miles? How about if you have 25,000 miles and your car is 8 years old? Are they saying that the fluid is now sufficiently broken down to warrant changing?
6. In a letter from ZF circulated to shops (see attached) it discusses "lifetime fill" and leaves it up to the car manufacturers' to decide what that means, however it does address the notion of what I am calling not-normal conditions. In such conditions it calls for 100,000 km or 8 year fluid changes. Yet another different recommendation!
7. Given all the above, the way I understand the recommendations is that the best option is to have a fluid analysis done in order to determine whether or not a fluid change is necessary. A company like Blackstone Labs (no I don't work for them) might be the best option, see attached sample report (thanks to the original poster of it in a different thread).
I don't have any of the answers, just wanted to post some of what I had discovered on this clearly complicated matter.
Confused yet?
Last edited by X5 Meister; 04-20-2010 at 07:22 PM.
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