My truck (2008 f350 126k miles, recently purchased from used dealer) has a dpf delete and I'm running a mini max tuner. Oil and coolant temps are around 140-145 when driving (50-70) degrees outside temps. Just did an oil and filter change. Ran the diagnostic on the truck, popped up saying an issue with the coolant thermostat. So I scheduled a repair (since I am not too engine wavy) by a local ford mechanic who now works for the ambulance company maintaining their vehicles. After I dropped the truck off, he noticed there is oil in the coolant tank. He is saying I need to replace the oil cooler. He also said once replaced to flush the system atleast 3 times using dawn. From my reading I've gathered there is a better fluid to use for flushing that can be purchased from a cummins dealer? My questions is, do you guys think replacing the cooler and doing the flushes will fix the issue? Or should I look at getting rid of the truck if the oil in the coolant (there was quite a bit of it) will lead to other issues yet to be determined? Thanks for the input..