2004 GMC Yukon V8 All Wheel Drive Automatic 101000 miles
My Yukon has been losing some oil pressure about 800 miles after an oil change. Concurrently, I have had to start refilling the coolant reservoir tank frequently. There is no sign of a coolant leak. Engine also has developed a loud knock at startup, 30 seconds later it is gone. The knocking is worse as oil pressure decreases which occurs as time passes from oil change. When checking or adding oil I have also notice some white residue on the oil fill cap. Definately feel like coolant is getting into oil. What could this be?