With my previous diesels, both IDI Ford's, I would plug in below 20* if available. Since picking up my CTD's, I have only had two nights where I wanted them plugged in, and it was 0 or below.

First night I had them plugged. And found out neither heater works!! My 97 will not start at all, cranks and cranks and cranks. Puffs a little smoke, but other than that nothing. Grid heaters work. 95 fires, rattles, and smokes a little bit, but runs. The 97 came from Texas, and the 95 from Oklahoma originally, then Iowa, so it doesn't surprise me that the heaters are inop.

 

My 97 has never failed me (granted I've had it for 2 months and its my first diesel), sometimes I remember to plug it in and sometimes I don't and it always starts just fine. And where I live it gets fricken cold down below 0. It does idle pretty low when its cold down around 500 or 600 for the first minute or so then it comes right back up to normal idle. So it sounds like if its stalling then something is wrong or out of adjustment to me. Oh ya I have 213000 miles on it too.

 

The 40°F plug in point is not a random number. For some reason, friction versus temperature really climbs at the 40°F line.

A timer works great for plugging in at warmer temps. I ramp it up from 2 hours to no timer based on the night lows. I think Bill (infidel) uses an ice cube temp sensing plug to regulate his block heater.

I just went out to plug in the truck without a timer. Overnight temps will be around -20°F. The power steering pump will howl, but the truck usually starts pretty well.
In the morning, I move the drop cord over to the mommy van for 2 hours and it starts very nice. The truck would not be happy with only 2 hours on the plug at these temps.

 

We had a light freeze several days ago, and my truck started fine unplugged.

I will have to run a 100' cord to plug, and haven't gotten around to it just yet.

I remember ice once or twice last "winter" and it started just fine, but would have been SWEET to have heat sooner.

 

I leave my truck plugged in all night as well and in N ( it has to for remote starter to work with manual trany )when it gets below -15 C, the reason i think your remote starter wont start the truck is (the remote starter) has a pre set pre-ignition time ( the time between when you push the button and the time truck starter cranks ) and it is set for too short of time for the colder whether, I dont know how to set the delay for ignition but would like any info possible ( polar start ), i have timed the time the wait to start light and the colder it gets the longer the wait to start light is on. I am on call and have been called in too many times in -30 C at 2:00 AM, truck always starts but it doesn't like it ( pistons and rings expand before cylinder walls ) could cause scoring ( just a chance but for a few dollars in power no risk ) a timer good for no oncall people

 

Good Info! Glad an Engineer chimed in. Explains why Cummins recommends plugging in at 40*.... and why big rig drivers do it!

IMO it's a mistake to say "My truck starts fine down to 20*, or 0*, etc., so I don't worry about it till then".
Starting is one thing.... frictional wear & tear is something very different.

RJ

 

I know exactly when the heat is on, have an inline thermostat set at 40° on the extension cord.
Mine is adjustable but as John said you can buy an Ice Cube brand nonadjustable thermostat from Ace Hardware for around $15. They come in several different temperature ranges and can be used in combination with a timer.

 

Hmm maybe I am missing the boat here? I have only plugged mine in once just to see if it worked. I live in upstate NY so we know about cold. Minus 30 and starts right up but might not be too good for it. Synthetics probably help but maybe I should be plugging it in.

 

If you plan on keeping for a long time plugging in is a good idea.
Saying your truck does fine starting below zero without plugging in is like saying you've never had a problem walking outside in your underware when it's below zero.
Sure you can do it for a while...

 

[QUOTE=Fueling around;1829919]The 40°F plug in point is not a random number. For some reason, friction versus temperature really climbs at the 40°F line.
QUOTE]

Im not arguing with you,but i see trucks with the 5.9 cummins that are 10-15 yrs old and haven't ever been plugged in once in.Most are on original starter motors,and if its well below zero,and one or 2 out of the 30 that are running won't fire,they shoot it with ether to get it going.I know because they leave the emptys all over the parking lot.One of my accounts they have uniform trucks,all with 5.9s ,and they all sit there and smoke cold,but they run,they dont even bother running eynthetic oil either,and these trucks run 400K+ before they get rid of them or do engine work(usually injectors nad head gaskets are all that happens to them).
Having seen this,and the fact that im running a 5w40 synthetic oil, I just dont see the harm in not plugging in my truck,until it gets very cold(10 degrees or less),ir if im plowing.

 

Good point. The Cummins engine is a very durable unit and takes a lot of use and abuse. I was just pointing out why they selected 40°F as the recommended point.

I usually don't plug in until the sustained temps are in the 20's. Now that daytime highs are teens and overnights hover around zero I plug it in (unless forgetting as last night). Sure it starts, but why not plug it in? Probably helps that my electric rates are less than half of many areas so the monthly bill doesn't scream at me.

-John

 

10f to 15f is where I plug mine in .... not for starting issues but it sure sounds better after it starts, below 20f they sound a little rough in case you haven't noticed

 

On my old ford powerjoke I think it had like a 1500 watt block heater on it, not 100% on that 1500 watt number I could be wrong thats just what someone told me. And if I did my math correctly it cost about 15 cents an hour to run 1500 watts so if you had it on a 2 hour timer it will cost you $2.10a week to run it. If it causes any wear and tear at all it would be by far cheaper to just plug it in a couple hours. I usually plug mine when it gets below about 25 degrees or so. Its a whole lot better than my old ford powerjoke that struggled when it was 50 outside. Just my .02

 

Oh my gosh! Why exactly did you leave Tacoma/Puyallup, John?

 

Probably should have used it last night. Overhead said 28 when I got in this AM.

I started after the heater light went out, went right to neutral and held 12-1300 fast idle for a while.

Ain't gonna be so cold tonight.