Cabin filter K&N or OEM BMW

I would NOT do the K&N engine filter. Little to no real world gain vs the investment. What I would recommend is the k&n cabin filter. I replaced the factory one with a k&n and makes a noticeable difference.

I saw a post online where the K&N cabin air filter gives you 30% more airflow.

I’ve had my i4 for over two years. Maintenance costs have been $0 but BMW gives you three years of free maintenance. When I have brought it in, all they do is inspect the car, top off wiper fluid and replace the in cabin air filter.

I have been using k&n for over 30 years, engine and cab air. I currently have a 4dr civic with 225,000 miles and a silverado v6 with 315,000 miles, both bought new. Both have had k&n filters since the first week of ownership. All have been cleaned and reoiled at least once a year, cabin usually twice. They all look great, and engines do not consume any more oil than when they were new. The savings in waste and money are ridiculous if you buy things and keep them. If you prefer to change vehicles frequently, probably not for you...

A fix is buying the k&n cleanable filter. It’s less restrictive but filters good enough.

Buy a K&N engine air filter and cabin air filter and replace them. They’re good for like 100k miles, you just have to take them out and bang them off in the trash every so often.

Yay. For cost and availability

They are cheap compared to others. K&N’s does not clean as well as I want it to and the HKS filters are super hard to come across (charcoal nano micro fiber????)

I've had to replace the cabin filter 2-3 times because of this problem. At first the smell would go away after replacing the filter, but eventually returns, usually when spring rolls around.

That was not replaced in the last 5000mi. If you have an itemized invoice, I would check to see if it states what part was installed.

Bosch with charcoal, DO NOT USE KN CABIN FILTERS, you’ll be very unhappy with them. Tried them for 4 years, sure cleaning was easy, but they did not filter any orders, if anything they made them worse. Switched back to Bosch.