Hey guys, first post here as I signed up hoping someone might have some experience in this!

I have a 2005 2.3l ford ranger which was giving me around 400 miles per tank in conditions of 10 degrees or above. I recently moved up north for work where temperatures are usually -25, and I'm barely getting 300 routinely. There are no changes to the way I'm driving, few hills, and less weight in my truck than ever before.

since I bought the truck, the temperature gauge has always sat at 1/2 between cold and standard operating temperature. I chalked it up to a faulty gauge or sensor but now I'm wondering if my thermostat is stuck open and due to the very cold conditions here I'm noticing the hit in fuel economy because the engine is so cold. Maybe in warmer temperatures it was at least warm enough to operate reasonable efficiently?

I've also noticed my hot air isn't blowing very strong or hot when the temperatures are super low which I would have thought might be more of a heater core issue but it does work no problem in regular southern Canadian winter conditions (ie 0-10 degrees)

Would love to hear any thoughts.

 

Welcome to the forum

You instincts are good, could be leaking thermostat, probably not stuck open all the way but not closing all the way when cold.

2005 2.3l Duratec doesn't used the Heated Thermostat housing like the 2003 and earlier did, so not too expensive to change on '05s


Engine Thermostats block coolant flow thru radiator until engine generates "extra" heat.
In cold climates radiators may never get "hot" or even very warm because engine metal and heater use is bleeding enough "extra" heat off.

So thats the way to see if thermostat is working, after cold start feel upper rad hose, it will of course be cold, turn heater on
After engine has run for a few minutes, say 3 minutes, feel it again, it should still be cold, NOT warming up with engine
Feel heater hose as comparison, heater hose WILL and SHOULD heat up with the engine

If upper rad hose is heating up that means thermostat is allowing some circulation thru rad.

2.3l Duratec has Lower Rad hose thermostat, so you can feel that lower hose as well, because you could get some convection heat in upper hose, i.e. warm coolant rises, most engines have thermostat on upper rad hose so you wouldn't get that convection transfer of heated coolant.

In some colder climates people need to put cardboard or similar in front of radiator to keep engine bay warmer, cold air flow in engine bay bleeds off engine heat faster than engine can generate it, so even if thermostat is OK engine simply can not generate enough heat when temps drop too low, so engine can't stay at operating temp.
Heater hoses also bleed off heat in engine bay so less air flow keeps them warmer and heater blowing warmer as well

You often see Semi trucks with zippered/snap-on grill covers for the same reason, to stop or slow down engine bay air circulation in cold weather to keep engine temps up


MPG
Cold air is denser than warm air, i.e. hot air rises, because it is lighter, not as dense as cooler air.
2.3l engine can suck in 2.3LITERS of air at wide open throttle, every 2 RPMs
A liter is a volume measurement
Air/fuel mix is a WEIGHT measurement
Gasoline uses 14.7:1 air:fuel mix ratio
So 14.7 POUNDS of air to 1 POUND of gasoline, or 14.7grams of air to 1 gram of gasoline
2.3liters of air at 32degF weighs more than 2.3liters of air at 70degF, that's one of the functions of a MAF sensor, it WEIGHS the incoming air

Since colder air weighs more computer has to add more fuel to get correct 14.7:1 mix, but you do get more power with colder air, that was the point of Ford adding Cold Air Intakes(CAI) on all their vehicles when they added fuel injection.
So the colder the air the more fuel is used, but it is not a great power curve, lol, because as temps get very cold you just use more fuel and not the extra power, so MPG goes down a bit.
The Double Whammy in cold climates is the gasoline you need to use is "winter fuel", it has "anti-freeze" in it, methanol/ethanol mix to prevent fuel lines from freezing.
Gasoline can't bond with water, methanol/ethanol can, and ALL gasoline has water in it, too much water is "bad gas" but all gasoline has water residue.
So gas stations use "winter fuel" in the winter months.
Methanol/ethanol doesn't produce as much energy as gasoline when burned in the engine, so power is less and so foot is down farther on gas pedal to get to same speed.
And MPG goes down.

Methanol/ethanol bonds with water and its freezing point goes down to -150degF or so, instead of 32degF, if water in your fuel line freezes then you are stuck where you sit until it thaws out, lol.
Methanol/ethanol also raise Octane level to prevent pinging/knocking in engines