Well I had a conversation on that subject when I changed from Ester to Synthetic. He was talking about the molecular structure not braking as fast as in conventional oil and that was the reason for the car running hot.
Don't get me lying, I'm not a scientist so his explanation was way over my head.
I have always used synthetic oil in my cars including a 350Z, however as we all know the 370 runs hot anyway.
What temps are you getting?