Something to consider is having an oil analysis done. I have Mercedes Benz engines in my work trucks and had an issue with a egr cooler going bad and needed to know if the engine had ingested antifreeze. The oil looked good to the eye, no antifreeze came out when the drain plug was taken out. The results confirmed that the oil did have antifreeze in it. The glycol was burned off and that is why the oil wasn't milky or show antifreeze in it. I learned that antifreeze has (sodium? don't have test in front of me.)in it. This is the byproduct left after the glycol cooked itself out. The antifreeze manufacturers add this to aid in showing the presence of coolant in engine oil. The cost of an oil analysis is 16.00 at a local lab here in Minneapolis MN. If interested do a search about oil analysis. Its interesting what you can learn about your engine.
Don
