I have explained in detail my thinking in post #14, I believe that change of oil in time is very important, but if You do it more frequently like every 1-5k miles, it will not extend the life of Your motor. Type of oil, design and condition of the engine, driving conditions, many things are to be considered. One guy posted on the Facebook the picture of the oil, drained from his truck after 3k miles, this oil was like a tar. The guy was trying to explain, that oil to be change more frequently. Yes, for him no doubt, something is definitely wrong. If the oil in my truck is in perfect condition after 5-7k miles, why do I need to change it? 10k is a limit for me.