I recently replaced my air filter, so I decided to wash the old one as an experiment. I used a bit of laundry detergent, and I added some washing soda booster. The wash water got really filthy. I tried to take some photos of the results (before and after), but it looks the same on the surface. Now I have clean filter ready when it's time to change it again.



Clouds of dirt starting to pour out the open end as soon as I dropped in the filter.





I just swished it around, and when I was done, the water was a very dark crimson color.







Before and after. Can you see more light coming through? Maybe not.







Before and after. The difference isn't very visible.