I am a new BMW owner, having bought a 2003 Z4 E85 2.5i manual transmission with 61,000 miles. I have read that the manual transmission oil is considered “lifetime” but I have also read that BMW recommends changing it at 100,000 miles. for my car which is 18 years old, is there any benefit or danger to changing it before 100,000? I have read changing it can improve shift quality.
Hello Mr. Randall, both statements are correct, most people confuse life time with life span. The expected lifetime of the transmission is 100000 miles, therefore, the service should be done at that time. There is no adverse effect to doing it earlier, I would actually recommend it. I usually use Redline fluid, it does improve the shift quality.
As far as service in general, I would follow Mile Miller’s schedule, here is a link: Lifetime Maintenance Schedule v03.13