I have a Shelby Dakota that has a working computer that controls the fans. They turn on at 204 degrees and off at 199 degrees. A 160 degree thermostat is in it. Rock auto says that a 195 was originally equipped. What would be best temperature to run.

The 195*. Engines run better when they get up to temp quicker.

X2 195* a 165* will open at 165 but temp will continue to go up. A 195 will open at 195 around the temp the engine was design for. never understood guy's thinking a 165 will make the engine run cooler it may delay it for a few miles but it still will go up.

I have a 160 in my 92 Dakota and it runs right over 160. So why would it not run 160 if it had a 160 in it? Mine does exactly that.

The thermostat doesn't stop the engine from heating up after it opens at it's rated temp. A 160* stat is open at 160* the motor will continue to heat up until it reaches it's normal operating temp. A 195* stat open at that temp and therefore the engine heats up to it's normal temp faster. An engine runs longer and with less wear at 195 then at 160.

I disagree. My truck won't climb above the 170 range even if I drive all day in 90* heat. Now if I turn my a/c on it will climb up around 190 or so but that's it.

That's because you have a very efficient cooling system. Most engines will heat up above 160 even with a low thermostat and won't typically level off until 180+, especially in hot weather. I think the point being made is that most engines should run closer to 190 since there wear out slower and get better fuel mileage, lower emissions etc.

Heat kills an engine. I've always run the coolest stats I can in my older stuff with great results. They preform much better at the 150 level than they do at the 195 level. I don't have issues with emissions or poor mileage either. The only advantage I see with a hotter engine is thinner oil. I don't care for oil that runs like water.

Well goose your results are great for race engines but terrible for street use motors I follow the recommendations of the experts and years of my own experience and run the 190* stat. A warmer engine runs looser and therefore less long term wear. Race engines are meant to run cooler because they only run for a short time and aren't expected to last near as long.