Here is a little background. 2007 f150 4.2 2wd auto 119,000 miles. I purchased the truck with 111800. At approximately 117500 the truck overheated. It was over 1 gallon low on coolant. I topped off the coolant and checked for leaks. I could not find any leaks. At 119000 miles I noticed my coolant reservoir was almost empty again. I topped off and thoroughly looked for external leaks. I could not find any. I changed the oil. I didn't see any water but oil did have some bubbles on top. I pulled all the spark plugs. They looked good. Yesterday morning I added a bottle of UV dye to the coolant reservoir. I drove the truck to work tonight. My motor oil has a faint glow from the ultra violet dye now . The underside of the oil fill cap really glows. So, the coolant is definitely making it into the oil. How do I diagnose this further? I thought the gasket problems were corrected on the newer 4.2 engines. I was just getting ready to sell the truck. I don't want to sell until I fix this problem.