There are no technical answers to your questions. ZF who makes BMW lifetime fill trannies, has representatives who will state (behind closed doors) that ZF considers 100,000 miles life time of synthetic fluid.

Most technicians agree that the life of a trans is limited above 100k if the fluid isn't changed. Based on the sum total of experience in technician groups, it is well established that applying a 60-80k interval can make a difference in the life of a transmission.

I personally think you have won the lottery getting 170k without service. I also would say that most techs are extremely reluctant to service a trans with over 100k on the fluid. This reluctance is not for the benefit of the trans it is to cover their A as anyone taking service to those levels will be the first to blame the tech when something goes wrong after the service. Who needs it, don't ya know.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician