Depending on your driving conditions, you are right. A thermostat alone will not lower the temps. Many users here have found lower temps in regular driving just by using the thermostat, but as you stated it will not help in stop and go driving. It will also be compromised by warmer driving areas.shade said:It was mostly for the AC but a thermostat wont make you run cooler unless you have air pushing through as well. So a lower thermo in stop and go traffic will only delay how long it takes to get up to normal temps.
Now a fan(or original fans turned on sooner)and a thermo combined will achieve the maximum cooling and keeps temps low.
It is also true that a fan alone will not lower temps below the thermostat controlled temp. It is my understanding, that the t-stat will keep the water in the block until it reaches the t-stat temp setting, then it cycles to allo cooled water in the radiator to flow into the block driving heated water out. The cycle starts all over.
Good luck with the wiring.