Purpose for different t-stat settings?

[SHOZ]

That would be pretty poor engineering IMHO. On the Gen Coupe the t-stat is in the water pump at the lower radiator hose inlet. The ECT is at the back of the head where the water exits the block. Flow is up through the block and through the head and out to the heater core with an auxiliary pipe going to the water pump.

It's very efficient and with a bigger radiator the temp seldom gets above 185F.

 

[GMBoy]

I would personally go with the 180. Still gives you good heat and it's hot enough to run the car well while also just enough cooler to offset any radiator or other issues you may have from sitting and age that may cauase overheating. It is true that hotter temps are better overall for engine wear, emissions etc but with older cars going a tad lower can be beneficial too. I don't do 160 thermostats though. My old 78b Jeep CJ calls for a 195 but I've used a 180 for the last 20+ years. Plenty of heat and it runs a little cooler on hot days on the beach or trail. I like the margin of safety of that extra 15 degrees.

 

[SHOZ]

When Hyundai bumped up the HP for the 2L turbo by 65 for the Gen Coupe they also bumped up the oil temp parameter for full boost. It was 150F then they went to 180F. They also added an oil/water filter mount heat exchanger.

The oil will take forever to get to 180F and if it's cold out may never. The Canadian guys could not get full boost during the colder months. Hyundai in the USA issued a TSB and an ECU flash to bring the trigger temp down to 160F but they never did in Canada. Some can get the dealer to use the US TSB flash and some cannot.