Hey, I am new here and this is my first post. I have an 07 Colorado with the 2.9 - 4 cyl. 198,000 miles, 2WD automatic. I am going crazy here trying to figure this problem out. There is tan sludge all over the dipstick to the point that I can't check the oil and just recently I found about a 1/2 pint of water in the resonator box! I changed the oil and filter 2X made sure the PCV openings are clear, checked the compression, (It is good) and even had Blackstone labs run 2 tests on the oil in which they did not find any coolant or water! It seems to be worse since the weather got cold. I just bought the truck last July and the seller told me about the tan sludge in which he could not figure out. Anybody have experience with this or any ideas? I sure would appreciate some feedback and thanks in advance!