Expert: John Kingery - 7/13/2010

Question
Hello,
I have a BMW 2003 325i (production date is 10/02) and it has about 101000 mileage.
Recently, I have changed the starter since it didn't start.
I am feeling like knocking on the wood since I didn't get inspections like inspection 1 or 2.
I have researched about changing the transmission oil. Even though BMW said that it is lifetime oil, many people change it every 50,000 miles or something like that.
I found out that my car has ZF transmission rather than GM which is weaker.
Should I change my tranny oil? or not?
I really appreciate your help.
Thank you.

Answer
I wouldn't change the transmission oil.

I don't put much stock in the "lifetime oil" claim either, but there are several problems with changing it:

1.  Since you can't drain it all out, you have to drain what you can, fill it back up, redrain, refill, etc.  The oil is expensive.

2.  An abnormal number of cars that have their oil changed have transmission problems shortly after.  Your transmission is running fine.  It's used to the oil that's in there.


If anything, I would check the level, and add to get it where it should be.