I have a 2016 Mazda 6 2.5L GT SkyActive. One day while driving, my car overheated while on the freeway. After getting the car towed home I started looking the engine over and noticed that I have coolant mixing with the oil in the engine. After removing the head I noticed coolant in the head on the lifters, you get the picture. I replaced the header seal checked to see if it was warped, it's not, all the way around. I also replaced the thermostat then closed it all back up. I hadn't had to replace the water pump since I had the car so I replaced it as well. Since I was replacing parts I wanted to replace as much I could while this thing was apart. I've replaced everything I know of on this engine. It's a simple design not much to it. I also did a pressure test on the radiator after draining all the oil from the engine. after applying pressure I didn't see any place where the oil could be getting into the engine. I also checked the spark plug housing, nothing. I loose the bolt on the oil pan and all I got was coolant flowing into my oil bucket. For this year and model of car does anyone know if this engine has an internal coolant pump or oil coolant pump or anything else that would cause coolant to mix with oil in the engine? I flushed the engine thoroughly, put in all new fluids, and it mixed all over again. Please help.