So, at 106,000 miles, I decided to proactively change my head before I experience any problems. So, I tore about the engine and once I got to the Valve cover off, I saw a huge amount of sludge in the valves. I mean, I have never seen so much. I change my oil at regular intervals, always use good oil. What do you think has caused this? Also, since I am installing a new head, should I start fresh with synthetic oil or stay with tradition oil? Any suggestions on what type of oil I should use? My car doesn't have any oil leaks either btw. Also, I am changing out everything since the engine is torn apart, water pump, timing belt, (I am even changing out the starter since I can get to it). Should I change out the oil pump or will the oil pump last another 100,000 miles?