Auto does a terrible job of keeping the engine cool. It seems in auto mode, it will never fully open.
Before startup, just knock the coolant door down to manual, and leave oil in auto so it warms up while on the ground. Once the oil passes 40C, flip the coolant door to auto. After takeoff, if you are going to do any fast and/or aggressive flying or climbing, fully open the oil door manually, but you can keep the coolant in auto.
With this, you can climb at ~175MPH IAS at 3000RPM and 55inches, though that is about the limit of it.