It seems that the demands on oil really depend on which area of lubrication one is discussing. So, why don't engineers isolate the lubricant between different areas. For example, why don't we have one fluid circuit for the crank and rings and a different circuit for the cam. Then, we can have two lubricants with taylored characteristics for the two different applications. It seems that this would not be different than current isolation of transmission fluids from engine oil. Am I missing something here?