The hotter an engine runs, the more power it makes. You want the heat of combustion pushing the piston down in the hole, not being dissipated through the cooling system.
160 degree stats don't allow adequate heater operation even in California. A 180 seems adequate in most of the driving I've done. If I lived in the snow belt, and frequently drove it in sub-freezing temps, I'd probably go for a 195.
The stock PROM has warm-up compensation into the 170's. With a 160, the system will never get out of warm-up enrichment because CTS never gets hot enough.
DesertSy has a 180. It runs in round-town driving at 182-184-ish on a Tech-1. I don't know what PrOM it has, but the IC pump comes on at 183, and is off at 182. So if I had a 160, the IC pump would never come on at all. No, I don't like the "hot wired" IC pump for several reasons, so I don't do it. I've observed that after a boosted run, CTS is high enough from the additional load that the IC pump is on, so it runs after an interval of operation at elevated (boosted) loading like it needs to, but doesn't run when it doesn't need to. Like during warm-up, or running down the interstate for hoiurs at a time during a cross-country trip.
And a last thought is that engines produced during this period (20-30 years ago) were designed with piston / wall clearances that were adequate to prevent scuffing during warm-up, but became tighter at "operating temperature" to ensure quiet running, and long engine life. That designed "operating temperature" was 195 degrees. Piston stability is crucial to maintaining the ring to wall seal. If the piston is rocking around because it isn't hot enough to become stable, blow-by at the ring results in lost power, contaminated lube oil, and increased wear.
Most SyTy's never leave the garage if they even run at all. So what the installed thermostat temperature is doesn't really matter. But for the handful of owners left that still drive their trucks regularly, there's some food for thought.
