So today I discovered that my 88 comanche 4.0 is dripping oil out of my k&n air filter. I only noticed it after 40 miles on the highway at 70mph. Is this normal? My 89xj 4.0 has some oil on its air filter but not crazy amounts.

 

Here's a full few of the air intake when it was installed on my xj. Had no problems with oil.

 

Well... I guess you'll save on maintenance!

Seriously though that's blowby that your CCV isn't sucking up. Check the rear valve cover elbow, hose, and intake manifold fitting for clogs.

 

Make sure all the CCV components are on there and functional like salad suggests. Grommets need to fit tight in the valve cover and they need to be clear internally. For about $60, you can get all that stuff new from Napa.

If you need to change your valve cover gasket, I have a mod that can be done to the internals of the valve cover to reduce the oil sucking into the air filter.

 

I'd swap out ALL of the CCV components. As cruiser mentioned, you can do the whole shooting match for around $60.

When the CCV system clogs up, the symptom is oil in the air filter. It's also possible to have that symptom with true engine blowby, but as the CCV system commonly gets clogged up and especially on your vintage, you need to start there.

I had the same symptom on my 88 Comanche. Removed valve cover, thoroughly cleaned and installed new grommets, reinstalled valve cover with new CCV hoses and problem solved.

 

I had just replaced the valve cover gasket 2 months ago when I got the motor running. It had blow by at first then went away after 100 miles after sitting 5 years with no head. I was gonna replace my gasket with a good felpro one. I hate the cork the gasket kit came with. All I need is a new vent line from the rear of valve cover to intake since the front is brand new.

 

x2 on what cruiser said.
Had the same problem couple weeks ago, did as cruiser suggested and now my filter stays clean!