This air filter thing is an interesting one. This may be tough to believe, but you can change your air filter too often. Air filters are designed to balance dust capture effiiciency and life. What does that mean? Well, a clean air filter lets more dirt through the element than a dirty one. Changing an element before it is really needed lets more dirt through the intake.

The trick is balancing the life of the element vs. intake restriction vs. dirt capacity. An intake restriction guage is the only accurate way to measure if an element is beyond its service life. Unfortunately BMW does not include one in the filter housing. (Believe it or not, our former 2002 Yukon actually had a restriction guage and in 60K miles it never moved showing the element had significant service life left)

I would change the element at the Service II interval whenever the message comes up in the display since we don't have a guage.

Just my .02

__________________
Dave

'05 325xi
'10 E70 35d
'85 911 Carrera
'66 911 Work in progress
'91 Chevy C1500
'95 Jeep Cherokee
‘18 Jeep JLU