Verify the temp with an IR thermometer on the thermostat housing.

If it really is running that cool make sure it actually has a thermostat in it.

 

How can I tell if it has a thermostat

 

Pull the thermo housing off and look...

 

What can happen from what I'm describing

 

FWIW, the FSM does not say what stat u must run, but it does say u must not operate the motor without a stat (except for testing).

 

Does your heater work good (make u sweat) when the gauge is pointing low?

 

This is what mine does as well.

 

Consequences of running cold

 

8 mpg...

 

If moving brings temp down its a circulation problem seeing how auxfan comes on and temp goes down that's a very good indication its air that missing from the equation . When was last fan clutch check up/replacement done ?

 

Never did one. But the fan clutch doesn't squeal?

 

The fan clutch is a air temp sensitive unit......it draws less air (free wheels more) when air temp is low, it draws more air (free wheels less, pulls more air thru the rad) when it senses higher air temp. Just because the fan spins and doesn't make noise, doesn't mean it is performing at 100% efficiency. If u don't know how old the fan clutch is, spendy the +/-$35 and take 20 mins to install a new fan clutch.

 

The 1999 FSM absolutely does:

THERMOSTAT
A pellet-type thermostat controls the operating temperature of the engine by controlling the amount of coolant flow to the radiator. On all engines the thermostat is closed below 195°F (90°C). Above this temperature, coolant is allowed to flow to the radiator. This provides quick engine warm-up and overall temperature control.

Additionally, the 1998 parts fiche specifies ONLY Mopar part 52028186 "THERMOSTAT , 195 Degrees"

I don't know about earlier model years on OBD-1

 

I just installed a new Mopar 195* thermostat last yr in my '96. Purchased from it the dealer. They could have gotten me 180*(severe or extreme duty?). Of course this was a yr ago.

 

I still don't see where it says "u must use a 195 stat". One would presume yes.......when the vehicle left the factory, it had a t-stat.....a 195. But again, the FSM does not say "u must use a 195 stat".......and nowhere in the FSM is 210 referenced as normal operating temp.

.......and the FSM does go on further to say "do not operate the motor without a t-stat, except for servicing/testing". It does not say "do not operate the motor with any stat other than a 195.......it just doesn't say that.