[old_master]

Check the PCV system, poor circulation causes this to happen. When the engine cools, condensation forms inside the engine and turns the oil into a milkshake-like gooo. The PCV system keeps the crankcase ventillated so condensation can not build up.

With the engine off, pull the PCV valve out of the rocker arm cover and shake it, it should rattle very freely. If not, replace it.

On the oposite rocker arm cover is hose, that hose is the intake for the PCV system. With the engine running, there should be a slight vacuum at the hole in the rocker arm cover where the hose attaches. If no vacuum is present, pull the PCV valve out and put your thumb over the valve inlet, there should be a strong vacuum. If not, follow the hose to the intake manifold and check it there. When you find and fix the problem, the rocker arm covers should be removed and cleaned out, they'll be full of that same milkshake gooo.