That's interesting.

The oft-claimed reason for changing transmission fluid is because of improved lubricity, ie it will prevent wear. Taking all those particles out. Improving sliding and rolling friction between moving parts. In that sense, the engine oil article is completely applicable.

Agree that it doesn't cover the subject of the additive package in the transmission fluid, and the friction modifiers.

I am a firm believer in preventative maintenance. I followed this philosophy for decades in the heavy equipment field. I apply it to my vehicles as well. Just not the automatic transmission fluid in my X5.

I've never had an automatic transmission problem either, since the restoration of a 66 Mustang that had a failed Cruisomatic transmission when I bought it. No problems after overhauling it.

I am not trying to talk you out of changing your transmission fluid. Each owner should do what they feel is right.

All I was pointing out is that many of the reasons given for doing regular preventative maintenance fluid changes on X5 automatic transmissions don't hold up to scrutiny. They don't have an economic basis. But not everything we do has to have a payback. Sometimes it just feels right.

As mentioned, there are two strong camps on both sides of this issue. It is always an interesting debate. I am on the side to change the transmission fluid every 50,000 miles.

I don't believe it is possible to have a valid study on either side of the coin that determines which side to join. There are too many variables.

I don't know how to include a bell cure endorsing anything unless there is a subset of that curve for those that change the fluid.

I can't consider the SAE study as endorsing your position either as I don't know what oil(s) they are talking about and moreover I agree with you--engine oil and transmission fluid are not an apple to apples comparison. As a sidebar I don't know about you but I changed engine oil a lot more frequently than I changed brake fluid on anything I raced and far far before 3,000 miles.

Since this issue is no more than a debate I am sure you can discount this logic----there wouldn't be a filter in the transmission unless there is a reason it should be there. If changing the fluid releases stuff that will harm the transmission, if I change the fluid every 50,000 miles that crap will never have a chance to build up. I will also be bringing the filtering parameters back to 100 percent of its intended capability. If it is lifetime fluid in a closed system there is no reason to check to see it has been overheated. That means if it has been overheated I could have a problem that could have been prevented.

I am not saying you are wrong. I am saying neither of the sides can definitely declare victory. And, since I don't know the parameter based on the lifetime position and there are several reasons that the fluid can be compromised, and a fluid change is endorsed under those conditions, changing the fluid every 50,000 mi. could contribute to longer transmission life. Since there are so many that have had problems that instigate this never-ending debate--and the possibility of fluid degradation is there, and there is no proof it causes a problem --the side of conservative caution is very logically justified as well.


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As you referenced we, who is we?

I have no problem with changing the filter if the transmission feels "sluggish". But I will carefully collect the fluid from the transmission, strain it, and put it back in with the new filter and just top off with the proper fluid.

2002 3.0 X5 243,000 miles
2004 325i 108,000 miles

Instead of listening to the marketing people from BMW you should follow the advice of whoever designed the trans, the engineers from ZF or GM .

I would guess that they would say to change the fluid at certain interval since as Engineers they know that to insure a long life for their products the fluid needs to be changed over a certain interval whether it be mileage or time.

In that specific post, it was myself and Brandon, but the phrasing wasn't intended to exclude others. The more the merrier.

The intent wasn't to declare victory. It is a debate for the sake of having a debate. The thread title was about thoughts on changing transmission fluid, and I only responded when I saw the old saws about there being no such thing as lifetime fluid, and that you have to change the fluid if you want to make your vehicle last. Those two aren't true IMO.

Well you'd never know. Most manufacturers say their transmissions are sealed units with lifetime fluid. This is what they told me when I bought my Tacoma two years ago. It also says on the tranny pan of our X5's that they are sealed units. Engineers from BMW and ZF have done hours of testing to advertise the fluid lasting a lifetime. It's just a gamble on whether or not to change the oil. That's all.

I thought I read somewhere that ZF recommends fluid maintenance on the X5 trans.

Let me see if I can find the article again.

As for the price of $400 for the oil changed at the shop....seems a bit low if oil used was OEM ZF at $25 per liter X 16 (including torque conv) ...just the oil totaled $400....my transmission shop bill showed 16 liters ... Is somebody here can confirm that a full flush need 16 liters ?

ATF/Automatic Transmission Fluid By ZF OEM 1 Liter 5HPXXX

The shop charged me cost for the fluid. Im sure they get it well below retail.