I don't see what the problem is, even with a 160. You don't need any programming to run a cooler t-stat. Closed loop comes in at 133 or 131 depending on year. If you are in an extremely cold climate, I can see a 160 might be too cold. But once you hit closed loop, the sensors are controlling fueling.

There should be no difference in fuel mileage going to a cooler t-stat. I have never seen any difference in any of the cars I have had over the years, just cooler operating temps.

 

I run a 195 in mine, and even sitting at a stoplight on a 100*+ day, I've never had it go above, or even get up to 210*. As long as your cooling system is in good shape, the temp shouldn't go much above what the t-stat designed to be set at. Which for these trucks is 195.

 

The problem is, GM spent millions designing the engines, and the engine and software worth both designed for 195 t stats. I know from it happening more than once, that putting a 160 stat in these trucks, will throw a MIL, as it never reached the operating temp programmed in the pcm. Captain Hook, who's knowledge FAR surpasses my own, has stated that the pcm will switch to closed loop at aroung 95 degrees, as long as certain other criteria are met. Your fuel mileage will suffer because of the lower temperatures and the air being more dense in the cylinders, which will cause the o2 sensors to pick up the added oxygen and fatten the mixture. At the same time, the pcm will also be at a different preprogrammed fuel map setting, further richening the the mixture. It isn't necessarily bad for the engine itself, but it isn't necessarily good either. Besides, why waste the money in gas and oil when you will not gain any performance, as the computer will still only have preset parameters to go by. Lower t stat and a tune will wake the engine up pretty nicely. Throw a nice exhaust and and a cam with that and you have a decent amount of power gains. Do any of that with stock parameters in the PCM, and all you are doing is giving the pcm different information so it can match to what it already knows. If it can't make a match, you have a check engine light. I may also be 100 percent wrong on this, but that's what my research and experience has led me to believe

 

a 180 thermostat wont affect much, a 160 will. On a fuel injected setup cold engine means it sends more fuel period. More fuel also means less mpg and worse emissions and shorter life of the cat. If you dont need to pass an emissions inspection then the lest to wont matter to you. These trucks arn't really fuel savers so the difference between any of these thermostats wont be noticed much. But hotter temps also help keep sludge from forming. GM has been running these engines for years, if they could all around improve it so much by just running them at 160 instead of 195 they would have by now. The only time I recommend getting a cooler thermostat is for example some 90's era chrysler products had 210 thermostats, those actually wern't good for the trans (radiator cooled tranny). But i believe there is a service bulliten about that by now

 

Personally I would have rebuilt the rest of the engine.

After 235K miles, adding new better sealing valves in the heads - you may find extra blow-by with those 235K mile piston rings.

I would have taken the opportunity to change to a low rpm torque-y RV-type cam, high volume oil pump, better dbl timing chain, better water pump, etc etc.

But that's just me.

 

the 235k miles is on the Dodge Dakota, the Chevy Blazer has 152k on it. The Dodge has never given a minute's trouble other than the water pump leaking around 140k. The old Dodge V8s, the pre-Mercedes Dodge, was probably the best engines ever made in America. I will stand by the RB (383-426-440) series particularly as being the best designed, and the LA (318) being the most dependable. The Dakotas never have fuel pump or heater core troubles, but the interior sucks compared to Chevy, and Dodge couldn't make paint to save their lives! My poor Dak looks like a calico cat lol.

I cant afford to rebuild the bottom end at this time. I'm figuring on doing a short block sometime next year, and transfering the new top end to it.

As a generic gearhead, not a Blazerhead, I know internal combustion engines want to run with their intake in the freezer and their bottom end in the heater. Transmissions don't like to be hot, period. To change the tstat in this truck isnt a big deal, so I may experiment with the 195 and 160 just to test the variation... and if it's great, I'll try a 180.

I live in South Carolina, so it's a WET heat! Like today, it's so stinkin' humid after these monsoon rains...

Im just trying to keep this truck running smooth as possible and long as possible. I'm looking at getting another 100k miles out of it.