What to look for / service around 75k miles

[JCL]

Originally Posted by kevinkay

Dealer suggests NOT to change lifetime transmission fluid, that it causes more harm than good?? I haven't done mine at 140k

I wouldn't say that it necessarily does more harm than good, but there is a gem of truth in what the dealer says. There is a well-understood risk of it doing harm, particularly if the fluid has never been changed. That is even if the correct fluid and filter is used, and the procedure is done correctly. Risk isn't an absolute, some owners will change the fluid and have no issues from the new detergents cleaning out the passageways and there being no place for that junk to go. Others will get a failure soon after a fluid change. It happens just often enough that many shops turn down those types of jobs (just like your dealer did) because they don't want to take the chance of having to pay for an overhaul that they have precipitated. Most BMW shops, Mike Miller, etc, will say to leave it alone at your mileage. I wouldn't touch it myself. Yes, I believe in preventative maintenance. It is just that a fluid change on a high mileage transmission does not reduce your risk or raise the chances that your transmission will go longer before failure. We aren't generally seeing transmission failures due to fluid failure. If we were, it would be a different situation. When you experience a failed transmission because you lose a sensor, or an actuator in the valve body, or something like that, you will have saved the money you would otherwise have spent on a fluid change, and come out ahead. And you can know that a fluid change wouldn't have impacted those types of components, which are the ones that seem to fail most of the time.

The rules of car maintenance are constantly evolving, they are in no way set IMO. We used to do points, condenser, rotor cap, and HT leads. Not now. We used to refill shock absorbers. Not now. We used to do 3000 mile oil changes. Completely unnecessary today in normal driving conditions.

The bathtub analogy makes no sense to me. The transmission system is sealed. Put a plastic seal over a tub of water and come back in two months. It isn't the same as if you were introducing external contaminants every day.

You also can't compare other vehicles directly. I maintained a Honda Civic and a Toyota Yaris for family members. 5000 km was an appropriate oil change interval based on sump capacity, oil condition, and engine design. At 3 years I had to do plugs, per recommendations (they were completely shot). On my last four BMWs, 20,000 - 24,000 km oil changes worked perfectly. No oil consumption. No smoke. Good oil condition at change time. Personally, I am glad to be living in an age when mechanical design has advanced so much compared to 20 or 30 years ago.