The factory ECU sets optimal ignition timing when the engine coolant temps are 87-100 degrees Celsius or 190-212 degrees Fahrenheit. Modern engine coolant temps are designed to run this hot because of the need for higher engine oil temps. Higher engine oil temps boil off moisture that may have accumulated during the engine at rest.... Also for emissions purposes and fuel economy.
I have done a lot of reading and self testing on coolant temps, trans oil temps and engine oil temps. Based on what my logs are telling me, my car tends to perform the best at 195-205deg F coolant temps, 210-220 engine oil temps and trans oil temps around 190. You want to keep the spread between coolant and engine oil temps under a 20deg difference, anything higher and something needs attention.