In a gasoline powered car/truck is usefull to use on a air filter a restriction guage or simply go by mileage/time?I have a guage on my air filter box or I can change the filter every 30K miles,Joe
The gage on my Ford Focus "lifetime" filter was in the green at 143,000 miles when I replaced the box. With the inlet duct in the fender I don't know how leaves got inside it.
I had one on my truck, but got rid of it since it never moved. The filter was probably still ok but it was like 5 years old so I decided to replace it. There is a little o ring at the base of the filter minder and I figured that was just going to dry out and start leaking anyways so I changed out the airbox for one that didn't have the minder in it.