Ok. After making several calls to different oil cooler companies it looks to me like -10 is all thats needed for high performance engines. Derale and Flex lite says -8 is all thats needed and never had an issue with it. Mishimoto only offers -10 coolers for 1000hp applications. Setrab likes to run biggest hose as possible, but says -10 or -12 is enough. -16 is way over kill was everyones responce. Hope this helps anyone interested .