We had to replace my daughters 4.0 Explorer engine after hers failed at 133,000 miles. The engine we had it replaced with reportedly had 62,000 miles on it. I have always changed my oil on our cars 3 - 5,000 miles. Obviously I have no idea what the engine's PO did. BUT - when I check her oil , on the dip stick there is crud - like small particles. I have changed the oil pan and gasket to get the junk out. I ran Pennzoil reg based (non synthetic) oil for 3,000 miles and change it yesterday to Motorcraft syn blend. I use motorcraft syn blend in my focus with no issues. Still see a lot of little particles on the dip stick. I guess this is sludge? I do not think I ever saw this in my other cars before. Any advice as to whether it may be sludge and what should I do to hasten a clean up? Thanks - RD