no wonder you have negative feed back on Premier Z.
How on earth can you monitor internal engine temps without the presence of coolant. The sensor has no direct contact without coolant, all you are measuring is air temp inside the coolant tube and will typically show low/normal. You can have hot spots inside and not pick up with the coolant temp sensor via consult. Running the dry without coolant for 5 min is excessive to me, maybe 1 min is OK. My car is fully warmed up in less than 5 mins with full coolant circulating as a reference.