In reality, how much dirt or solid debris is in your engine anyway?
Engines ran for half a century without oil filters. Frequent oil changes were/are really all that's needed. If you have metal in your oil, you have bigger problems to deal with.
I've always been curious about such matters and many times I've taken a hacksaw to spin-on filters and have also cut open paper element style filters on all kinds of cars.
I've never once found "dirt" or anything that would harm an engine if it weren't filtered out. I'm a stickler for the 3000 mile change interval on all cars regardless of age.
Recently, however, I changed the oil in a 2008 Honda that has a light on the dash that tells you how much oil life the oil has left in it. It decides this by tracking driving habits, engine hours, miles, etc to determine the optimal time to change the oil. This oil change was 8500 miles.
I opened up the filter and it looked practically new. Oil was clean and there were no rocks, marbles or bowling balls present.
Under normal driving conditions on a well maintained engine, I don't think there's really a need for an oil filter. It gives us peace of mind, though.
The real engine killer is blow-by gases rather than solid materials floating around in the crankcase. Frequent changes are the best way to deal with that problem.
