[621Ranger]

Your engine has two stats sitting next to each other. Two different temp ratings... one opens before the other. There likely aok with the low miles you have.
The first thing I would do is make sure the routine service is done. You already have the mouth piece coming... thats good too. Other alterations you need to think about. If you run a tuner you should also be adding gauges to monitor your exhaust gas temp and boost. I have a good friend with an 05 LLY and I have the LLY.... his is bone stock and gets 19 MPG and runs great... I played with mine and the motor is now on my engine stand getting major service... Just food for thought.

 

[621Ranger]

David04 is correct... Mine looks like a orange coil on the upper left in the instument cluster... I think it stays on longer as temps get colder. Just turn the key on and wait for the light to go out then start.
P.S. Your mileage will improve with warmer summer temps and summer blend fuel. 17 to 19 MPG is not uncommon.

 

[621Ranger]

The glow plugs work well... as low as 35 below zero and block heater not plugged in my truck has started. Glow light stays on about 3 to 4 secs at that temp. I run Mobil Delvac synthetic oil and I'm sure that helps too... Good Oil... @ 107000 miles and the inside of my mode looks great except for the blown head gasket I would recommend plugging the block heater in though for below zero temp if you can get power to it... Just easier on the motor I think from the sound of things at a 25 to 30 below zero temp start up.

 

[621Ranger]

If the coolant level is stable @ the full mark; the temp warms normally and temp gauge rises gradually as it warms you should be fine. My 05 lly was running just above 180 on Friday with temps in the 30s and Sunday with temps in the high 50s it ran around 200.

One simple test to do now and before your warranty goes off is to fill reservoir to the neck and idle the cold engine with the coolant cap off; watch for bubbles in the reservoir. You should Not be seeing any continuous bubbles perking up to the neck. Continuous bubbles would be an indicator that combustion chamber gasses are leaking into the cooling system. After 5 minutes you can suck out the excess coolant or just put the cap on and the excess coolant will go out the overflow.

Not a bad idea also to make sure the radiator core is clean every 80 to 90 thousand miles... cotton wood seeds, pollen, dirt and leaves can get stuck in and on the fins of the radiator. Wash with garden hose spraying from fan side of radiator to front and spray from top of the front downward. Best to pull upper fan shroud and fan too if you can get it off. Have your mechanic friend help or send to a garage (billable time should be about 45min) if you would rather drive your truck than work on it.