1996 Dakota 2WD with 3.9 V6 Magnum EFI, Manual Transmission, and AC with only 90k miles. I'm replacing the Timing Chain due to noise/slop, figured I'd replace the Water Pump, Fan Clutch, and Thermostat and flush the cooling system while I'm there. I've looked through the forums and found one mention of 195* T-Stat recommended indirectly when addressing coolant type, but would like to confirm since that sounds high for that old of a truck. I'm planning on using the plain old green Peak brand coolant. I live in the central US with temps from single digits in the winter to triples in the Summer. It is a daily driver, no towing, just light-duty hauling, not looking for high performance, just reliability. Thanks!

 

That's what the computer wants. Since you don't have a choke, the computer injects extra fuel into the engine to warm it up. That's called "open loop" mode. On carbureted engines, a cooler thermostat will make a richer fuel/air charge. On a computer controlled engine, it just wastes fuel. Between a new timing chain and a proper thermostat, I've seen signicant increases in fuel economy.

 

Thanks, I get that EFI like to run hotter to take advantage of better fuel atomization. Not sure how the hotter T stat makes a difference at startup when the engine is cold, but I’ll order the 195 degree and note my current temp on the temperature gauge and see how things go this summer.
BTW: I’ve been averaging 17 MPG which is disappointing for a small truck.

 

I use a 180 because with the recommended 195 the motor gets too hot for me in summer with the AC on. Same truck as you but a 94 that had 140k miles when I got it. It was still getting hot after I fixed everything TC, water pump, plenum, exhaust, etc.

 

On the topic of thermostats, I have a funky thing going on with my cooling system that I'm not sure of the cause. I put in an OEM thermostat and the short coolant hose some 10 years ago or so while I had everything ripped apart working on other stuff (nothing wrong with the original thermostat). Worked no different than the original until 1-1/2 years ago when I flushed my coolant system (including the heater core) and replaced all the hoses including the heater hoses. Since then, the needle on my temp gauge in the dash climbs to 11:30 then drops back to 11:00 where it remains steady. I have no idea why it does that. I'm assuming the drop back occurs when the thermostat opens up. Anyone else have this situation?

 

Normal behavior.

 

If you may need a timing chain, that will cause it to run cold and suck fuel. I had a '94 Ram 1500 with the 3.9 that had major chain slop noise. I had been getting around 16 mpg. Poor acceleration, almost no heat in the winter and so on. A new timing set along with a 195 t-stat and my mileage went up to 26 and the heat would cook you.At first I wondered if someone was messing with me but between a fence, dogs and security cameras, nobody was adding fuel.

 

I'll think about it. MPG is my only gripe about this thing. Not that it got good MPG before I put the 180 in there. I think I put a 195 in when I had the motor open to do the plenum, tc, wp, etc.