I just replace the engine in my 13 Traverse awd. the old locked up and when we removed the heads and oil pan there was a large amount of sludge in it. My questions is is there a synthetic oil with a sludge cleaning agent that i could use. My mechanic says these engines are notorius for having oil in the blow by which leads to the sludge. Help I spent over 6,000 for the motor and install. the old motor had 110000 on it. I bought it used.