Top critical review
Report after 2-month testing - READ THIS
Reviewed in the United States on September 28, 2019
I have been using Bosch air filters forever, so never thought I'd give a negative review on one of them.
As many other reviews pointed out, the air flow will significantly decrease compared to a non-HEPA filter. This is totally expected given the extreme level of filtration.
However I couldn't find a review that tried to quantify the air flow difference. Having just switched back to a regular P3875WS on my 2016 Honda CR-V, I can say that the airflow with the HEPA on max front vent is equivalent to about 3-clicks up with a non-HEPA filter. This is huge!!
As a consequence, on a hot Californian day where the car has been sitting with 100F outside, cooling down the car will take at least 10min. The best alternative being opening the windows... which defeats having a HEPA filter!
Now, when it comes to filtering the air at a HEPA level. If you do long drives without getting out of the car, there might be a benefit. However for short drives or frequent stops with door or window opening I don't think it makes any difference in the air you breathe.
I was also shocked to smell the cigarette smoke from the driver in front of my car, I assumed a HEPA filter would not let that through (but maybe I'm mistaken on this).
Anyway, after 2 months of use and grinding my teeth for the lack of air and fan always on MAX, I decided to finally order a standard cabin filter and switch back.
When I removed this HEPA filter I noticed the shape was a bit distorted, and it showed damaged at the bottom in the center. What happened is that the blower tries to suck more air than the filter can let through, as a consequence it sucks the filter in, making a bow in it. And the down-most spot (center) touched the blower spinning axle, almost poking a hole through the filter.
So for all the reasons above my conclusion is that this filter is not worth the hassle, at least for my car. Your mileage may very.