There are a lot of opinions on the thermostat and the size of the lines. The bigger lines and the removal of the thermostat had more to do with less restriction in the oil circuit. The 2015 coyote has a heat exchanger that I did not remove. That will allow the oil to be heated with the coolant to a point. My cooler is on the small side as it is only a 16 plate cooler. It is always a trade off. I decided to call Ford Racing tech line for confirmation. They suggested -12 lines instead of -10 for the coyote. They said -10 was marginal but -12 would be better. They did not recommend the thermostat. I don't really know any more than that. I don't think the thermostat would hurt you, I just didn't want to take the chance after my call with Ford.