[FrankChastain]

Thanks guys for the comments. One reason I posted was I have noticed on my wife's TrailBlazer, straight line six, is sometimes you hear a nock or bump when you start the car up, not it the morning, but other times. As I understand there is a valve, in the filter, that keeps oil from draining out of the block so to have oil in the block for start ups. This is what I understand. The engine never did this until about 3 or 4 changes ago. I change the oil and filter every 3000 miles. Please correct me if wrong.....and again thanks..frankchastain

Please keep in mind this is a personal use car.....