How about this. A 180 thermostat will let the engine run cooler if there are no other problems with the cooling system or engine causing it to over heat.

 

My question is why cooler is better. I assume that the engine was tuned to run at 192-195 degrees. Running cooler may not necessarily be better for the engine. A 15 degree drop is a fairly large drop and in the summer time can you maintain 180 degrees? I am sure you can in the winter, but that seems like a challenge in the summer. Temperature fluctuation can't be good either.

 

I took this off of the Hugh's web site;

"From the laws of Physics, we know that cooler air is denser than warmer air, and since horsepower increases as the amount of air and fuel burned increases, cooler air makes more power. Replacing the factory thermostat with the low-temp Thermostat will allow the engine to run cooler, making more power and reducing the engine's tendency to detonate. Detonation, usually producing audible pinging or even knocking sounds, refers to the spontaneous explosion of the unburned air/fuel mixture in the combustion chamber. Detonation violently ends the normal combustion process, reduces power, and can severely damage the engine."

 

A 180 degree thermostat starts to open at 180. Is fully open at or near 200 degrees.

 

Actually, it does. My truck was running hot, put the 180 in, and now it does not run hot, it just runs to cold.

 

an in between 180 and 195 tstat would be nice. like 188
no CEL from running too cold and not as hot as stock.
I'm drinking...uh I mean thinking about the 3 bears story.

 

My dad has a 1973 Chrysler Imperial with a 400. It was running hot and driving him nuts. He checked for blockages in the block, replaced the core plugs, and even went to a colder t-stat. It still ran hot.

Finally, on a whim, he checked with a knowledgeable radiator salesman who inspected the radiator. Flowed fine. They checked the book. Uh oh, the car had the wrong radiator in it. The cores were too small, hence causing the overheating problem.

He installed the correct radiator, the correct t-stat, and now that car will idle all day and not get hot.

So you are incorrect, a lower temperature t-stat will not correct problems with a vehicle running hot.

 

Yes that true if the car has a radiator that is too small to cool the motor. No thermostat, miracle radiator fluid or anything will help when the basic components are mismatched. Changing to a cooler t-stat will not solve an overheating issue caused by other component(s). Its a mechanical valve with a bi metal spring treated to contract or expand when certain temperatures are reached.
However if all the components are properly matched and maintained and the thermostat is changed so that it opens at a lower temp, the coolant mixture in that system will run around that temperature. You can have temp spikes under severe loads with or without high ambient temps.
FYI: Make sure your radiator cap is holding 16 psi. It's amazing how the slightest loss of pressure plays havoc with todays vehicles.
I believe the original question at the start of the post wasn't actually answered. The reason Hughes recommends a 180 degree stat is two fold. At the risk over oversimplifying, you're trying to convince the PCM it's December when it's July outside. This causes the PCM to enrichen the fuel mixture slightly in a vehicle on the edge of detonation already. Secondly this may promote a slight power increase, especialy if other components are changed.
This should also give you an idea why you can't use a low temp stat in a PCM equipped vehicle.

 

Well said dsertdog!!!

 

A thermostat regulates the temperature at which the motor will operate... you overall cooling system will determine how well your able to regulate that temp. if capacity is reduced, your system will run hot (plugged radiator), if your fans are not drawing enough airflow past the radiator in reduced speed conditions your system will run hot... plain & simple.

Gary if your truck is running hot, take a few steps back and think about whats going on... get a temp sensing gun and measure the input & output ports of your radiator and then compare it to a truck that has no heating problem (from a cold start idle, let the t-stat open up first before measuring). if you get the same temp in but a hotter temp out, the either your rad has a plug in it or your clutch is not engaging fully on the fan.

edit: you should also check for exhaust in the coolant...