All the cars I've owned have had cabin air filters. I check it every four to six months and if it's not too dirty, I clean it by hand; if it's filthy and/or one year old, I replace it with a brand new one. My boyfriend's truck has been in the shop for the past two weeks so he has been driving his mother's car. I noticed it smelled kind of musty in the car so I asked him when the cabin filter was last changed. He had no idea what I was talking about, he had never heard of a cabin filter. If you have a vehicle that has a cabin filter, do you clean and/or replace it on a regular basis?