Closing the slits in the valve cover and installing a PCV system is really one of the best things you can do to keep contaminants out of the oil, then something that filters 12% of the oil (bypass) might make sense as insurance.
The problem with our motors isn't the design as much as it is the design. What I mean by that is slits in the valve cover in this part of the country is insane. Even paved roads have a large amount of sand, topsoil, etc and all of that is being sucked into the engine at road speeds. With the high winds we get on a daily basis, there is dust in the air all the time. Where does all that crud go? Some of it stays in the top end and fills the rocker tube assembly with dirt along with the rest of the passages. Nevermind what it is doing to the cylinder walls.
How many questions do we get asked here about how to clean out oil passages, or why there is no oil going to the rockers, or why a push rod is bent. Every engine I have taken to the machine shop has had a mostly closed internal rocker tube passage. Maybe its just Kansas, but that is how it is here.
This is not a "FOR" or "AGAINST" oil filter post. It's a You do the Math and decide for yourself post. Closing the system as much as possible and installing PCV is just a good idea. And if you want to do it for much less, order the parts and do it yourself:
http://devestechnet.com/Home/PCVInstall
