I changed the engine oil in my M109 today and noticed that the oil which drained was awfully thin (almost like water) and there seemed to be a lot more of it than I remember from previous oil change. It looked like it was diluted with diesel fuel, there was probably two more gallons than there should have been. I drained the oil cold and it should have been thicker than this. did not see any milky mixture indicating presence of coolant or water. If it is diesel fuel, what is the probable cause? Leaky injectors? Leaky injection pump? Is this problem common? What should I check first?