Hmmm, never changed a cabin filter; don't really see the point.

The point is cleaner, fresher air, reducing dust in the cabin and less strain on the heating/AC system

As with any other sieve type filter, the air coming through an old filter is cleaner than the air coming through a new filter. Said another way, a clean filter means less clean air in the car.

"As with any other sieve type filter, the air coming through an old filter is cleaner than the air coming through a new filter. Said another way, a clean filter means less clean air in the car."

Excuse me, Shipo... but that makes no sense. Please enlighten

Try this:

• Take a colander and line it with cheese cloth
• Squeeze the juice and pulp and seeds from say 10 lemons
• Now pour the juice, seeds, and pulp through the colander lined with the cheese cloth.

Initially you'll see reasonably pure lemon juice flowing through at a good rate.
As the sieve gradually clogs two things happen:

1. The lemon juice becomes much more clear
2. The rate of flow through the sieve is measurably reduced

The above example illustrates exactly will happen to any other sieve type filter, be it an oil filter, an air filter, a fuel filter, or even cheese cloth in a colander.

Interesting comparison... sorta' like oranges and baseballs.
Air and liquid are two different elements with obviously different functional properties
However, no need to continue the debate... once again, 'to each their own'. For me, I'll change my car's cabin filter per manufacturer's recommendation

When you study "fluid dynamics", there is no distinction made between gasses and liquids (at least not within the context of filtration). The same thing applies here regarding sieve type filters, regardless of whether the flow being filtered is a gas or a liquid, the analogy stated above applies exactly.

• Fluid dynamics - Wikipedia, the free encyclopedia

You said it - it's the balance between the better filtration vs. the reduced flow rate.

The other thing you didn't mention is whether the filter picks up anything like mildew that stinks up the cabin.

Not just personal preference, but it depends on where you live. Humidity, mold, mildew, dust, etc...

To be sure if my cabin filter started to smell, I'd change that sucker in a heart beat. :)

So be it, indeed you may have a valid argument concerning flow dynamics. Regardless, my personal preference is to change the filter and I use the granulated charcoal type

Wishing you, Shipo, and all members a happy and productive day