Denny and several others have stated before that proper heat into the system on the cooling side id important. Proper combustion is most effiicient between 180 and 220 degrees at the coolant side of the operation. PCV and total control of burn rates operate more efficiently at these temps. Temps within the rest of the engine are a concern also but for the guy whom wishes to just have a good ride and enjoy, keep the coolant levels (temp) where you know where it likes it. I replied because you posted a good question of why such a difference. You're good to go.