aklim,

I can tell if my filters are clogged with out removing them. All I have to do is drive up a hill.

Where is the o-ring on a primary filter, or a the secondary filter for that matter? My prefilter is held on and sealed by 2 worm gear clamps. But maybe yours is different.

Sounds like U change your filters about 10 times as often as I do. So since both of them cost about $10, that's not $3.56, its About $100. Maybe U have money to throw away, but I don't.

AND filters get more efficient as they get loaded and are good up to the point they impede engine performance.

I got a winter car (300SD) and never changed the prefilter. It lasted 70,000 miles then I changed the engine to another car because 1st one was rusted too bad. Guess what, same filters are still in there.

If it ain't broke, don't fix it.

P E H