BMW Lifetime Transmission Fluid
The fluid BMW uses is also known as lifetime fluid (not forever fluid). First let me explain why: In general, transmission Manufacturer's for BMW's are better built. It's either a zf or gm transmission depending on what model you have. 3 series commonly uses gm and 5 and 7 series uses the zf. I believe the lifetime fluid was introduced back in 1999 as I can remember a synthetic formula of transmission fluid was used. This fluid is less prone to chemical and viscosity break down compared to conventional oil. It was 3 to 4 times more expensive and it was suitable for up to 100,000 miles. This is why it was called lifetime but I think it should be called “long-life”. When working at the dealership we always had requests to change out the transmission fluid. It was recommended as a no-no because due to liability reasons, if the transmission had shifting issues in the future, the dealership would be responsible for it.
Well my take on the fluid change is still a 50/50. Being an independent shop, we only see cars out of warranty especially over 100k miles. In my opinion, automatic transmissions are never meant to last forever because the inside of the transmission has many paper thin wafers known as clutch plates that will wear out eventually, resulting in hard shifts or slips. It really depends on the transmission and your luck. When new fluid is introduced in the transmission, the old material / fluid viscosity gets wiped out and drained out. As the new fluid settles in the transmission, it may become too slippery for the broken in clutch plates and seals, causing low fluid pressure resulting in slip. This is why it becomes such a liability.
The other 50% reason why to change it, is if the old fluid stays in the transmission too long, it may lead to transmission shifting issues and failure as well. As viscosity of fluid breaks down it does not have the chemical properties to lubricate vital transmission components and also keep the transmission cooled down. Temperature overheating is the number #1 cause of transmission failure!
Here at Bay Diagnostic our thoughts on transmission fluid change is: recommended every 60 miles (it is the smart way to protect you $$$). If you do not know when the last time it has been changed or you have over 100 miles, be prepared. If you are not prepared to invest in a transmission whether its 6 months down the road or a year, don't do it. Unless the car already has a shifting issue, there is nothing to lose. This is always how we advise our customers when it comes to this type of service.
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