I am approaching the annual OCI on my 2012 F30 335i BMW. As it is currently laid up with a bum charge pipe, I decided to change the cabin air filter when it arrived in the mail yesterday. I put in a Mahle LAK812 to replace the Mann made OEM filter that was in the vehicle. There was no apparent difference in manufacturing of the filter media, with the only visible difference being that the side plates are plastic on one and syn fiber on the OEM.

The dealer had installed the last filter in backwards, but at least it had been changed during the free maintenance period. Manufacture date was 7/2013 and the filter felt heavy coming out of the car. For a small filter, it came in at 11 ounces. I also noticed that the filter is installed around a curve, which squeezes the pleats on the downstream side of the filter.

Does anyone have insight as to any reason to do this and what impact it has on filter flow??

I figure that it was simply a matter of getting a good size filter to fit into the area that they had available...

Since filters are designed with an airflow in mind, what difference would installing it backwards make on the past few years of use since the dealer installed it?

picture on the scale below. It is run in mainly recirc mode, but a good amount of brown discoloration can be seen on the media. Additional pictures can be done if anyone is interested before I toss it.