I thought long and hard about the possibility that a slug of oil in the middle of a pipeline with lower viscosity, could because of it's lower viscosity increase the flow rate by pulling untreated oil up line and pushing untreated oil down line. I am sorry, it is wishful thinking but not possible. I have to admire your perseverance 'Alkaline', you should study fluid mechanics, you have a very inquisitive mind. Read my previous posts, pick up a book on fluid mechanics; you will eventually agree with my conclusions. My background: I studied fluid mechanics at University a requirement for my degree in Engineering. I worked 7 years with the Institute of Sedimentary and Petroleum geology and another thirty years managing 40 dams and 36 reservoirs using mathematical flow routing, optimization and risk management models.