Here's the situation. A female friend wants me to change oil in her '03 Cavalier. It has that goofy filter screwed into the valve cover as I think the 2.2s do. My quandry is what happens if these filters become plugged? Do they go into bypass like a normal filter? The reason I'm asking is that her oil hasn't been changed in a LONG time and I want to re-fill it with either Mobil Clean 5000 5w-30 or new Pennzoil High-Cleaning 10w-30. I want to gently clean the engine without dislodging a ton of dirt and sludge and plug up the filter and blow the engine. Any suggestions would be appreciated.