Quote:
Originally Posted by bcredliner
 The certification of the specifications would take brand out of the equation. As I interpret your post-- what is on aftermarket product is not certified so it is not a necessarily a match to BMW fluid. For that reason your recommendation is to use BMW Fluid. While most of us have a brand preference from past experience and we may have used that particular fluid with satisfactory results in an X5 tranny, that is not the safest way to go. Did I get that right? |
Since BMW don't have their own fluid (it is a ZF fluid spec, since ZF built the transmission) I would leave BMW out of it. I think it needs to be a fluid that meets the ZF Lifeguard spec (5 or 6, depending on the ZF transmission under discussion). The fluid could be from BMW, VW, Audi, etc, or from ZF themselves. It could also be from a major oil company like Shell, Castrol, Pentosin, etc, if the fluid in question was certified to the ZF spec. Many of them are.
What is available in the aftermarket other than the certified ZF fluids are a variety of generic fluids that their manufacturers claim will do just fine in a ZF transmission. And they may do so in some applications. Certainly some posters here have had good results with the non-ZF fluid they bought from time to time. But that is where the risk is. I think ZF know more about the fluid requirement than a distributor who blends ATF himself. And some major oil companies are selling a certified fluid alongside a different generic fluid (but with the same brand label) that is claimed to work in everything from a Toyota to a BMW, covering four or more different transmission manufacturer' fluid specs with a single fluid.
We all have our favourite OEM suppliers. I like Castrol myself, I have had good results with their products. But when I use a Castrol motor oil in my BMW I know that it meets the API SM or SN spec, and that it is also an SAE 5w-30. There are standard tests available, and those two specs provide a baseline. As much as I like Castrol as a supplier, I won't use a Castrol ATF in my BMW except in my power steering system, where it works fine. Castrol don't sell a certified transmission fluid that ZF has tested, at least not in my market. They certainly may do so in other markets.
What alerts me to the risk with the Castrol generic multi-vehicle ATF, just as an example, is that they claim it is a Dexron compatible fluid, and also a ZF Lifeguard compatible fluid. Compatible, not certified or tested. But we know that Dexron fluid (true Dexron) doesn't work in a ZF 5 or 6 speed transmission. The problems have been documented. It has to do with clutch engagement points. I know from experience that manufacturers fine-tune ATF recipes to resolve shifting issues, usually with friction modifiers. They have even shipped out the friction modifiers in small bottles to dealers, to add to a transmission that is exhibiting shifting problems. So I believe that the friction modifiers that they incorporate can matter. I am left with the conclusion that this generic fluid either isn't really a ZF compatible fluid, or it isn't really a Dexron compatible fluid. One of the above is true. Both cases are problematic IMO. Not taking anything away from Castrol here, but they, along with many other oil companies, use the phrases "certified to meet xxxx" and "suitable for where xxxx is called for" and the phrases are not the same. It doesn't mean that a generic fluid will cause a transmission to blow up, we know that isn't true. But it does mean that the DIYer or shop that uses a generic fluid in place of the certified fluid has decided to accept that additional risk. I just think there are enough risks with these transmissions without adding to them. All IMO.