how cold before plugging in block heater
Logistics Pro
Joined: Mar 2007
Posts: 4,604
Likes: 4
From: Claremore, OK
It's up to you. Assuming your batteries & glow plugs are working normally, you can go down into the teens before worrying about it. But on the other hand, if you plug the block heater in...your engine is warmer quicker (heat in the cab, cleared windshield). Plugging it in now won't hurt anything except your pocketbook (electric bill).
I'm hitting easy street
Joined: Nov 2009
Posts: 6,395
Likes: 27
From: Central Oregon
A non-scientific test to show how the block heater can heat your coolant.
(to have clearer windshield you must have the heater set to defrost and temp control on high)
My truck likes to be warm. So, for me, 30* and lower for my truck. And all night.
You can get a heavy duty timer to plug into and have it start 3 hours before you need it. Now the above test was at a pretty warm temp, I haven't seen anyone post from a lower starting temp. (Too cold to go out and write down temps, which, I don't blame them!!!)
(to have clearer windshield you must have the heater set to defrost and temp control on high)
This morning I plugged the block heater in. My Scangauge read 39 degrees.
1 hour later it was 80 degrees.
2 hours later was 94 degrees.
3 hours later it was 103 degrees.
4 hours later it was 110 degrees.
5 hours later it was 116 degrees.
Yes, 39 isn't that cold to start, but was interesting to see that it went from 39 to 80 in an hour.
Currently my oil temp in hour 3 is 77 degrees. It was 40 at starting point.
Oil temp after 4 hours was 91 degrees.
1 hour later it was 80 degrees.
2 hours later was 94 degrees.
3 hours later it was 103 degrees.
4 hours later it was 110 degrees.
5 hours later it was 116 degrees.
Yes, 39 isn't that cold to start, but was interesting to see that it went from 39 to 80 in an hour.
Currently my oil temp in hour 3 is 77 degrees. It was 40 at starting point.
Oil temp after 4 hours was 91 degrees.
You can get a heavy duty timer to plug into and have it start 3 hours before you need it. Now the above test was at a pretty warm temp, I haven't seen anyone post from a lower starting temp. (Too cold to go out and write down temps, which, I don't blame them!!!)
Lead Driver
Joined: Feb 2011
Posts: 8,241
Likes: 155
From: L.A. (Lower Alabama)
I don't think there is a set temp for this. Our trucks have a little different "personalities" on this issue based on miles and wear and fuel etc. Just pay attention to how it acts at different temps. There is likely a temp at which it cranks a little slower or cranks longer before it fires up or just takes longer to smooth out at cold idle. That would be the temp to use the heater.
Senior User
Joined: Mar 2008
Posts: 176
Likes: 0
From: Toronto, Ontario, Canada
I'll plug it in if it's 0 F or colder - the block heater is on a timer so it gets 3 hours before startup, seems to be enough to make the difference. To keep it energized all night would be (expensive) overkill I think.
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Senior User
Joined: Apr 2009
Posts: 359
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I go 30 or below more because my truck REALLY seems to like it. I use a heavy duty timer clicks on at 2am and when I get in it at 5 she purrs like a kitten.....
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Posting Guru
Joined: Jan 2008
Posts: 2,408
Likes: 0
From: Trenton, MI
A non-scientific test to show how the block heater can heat your coolant.
(to have clearer windshield you must have the heater set to defrost and temp control on high)
My truck likes to be warm. So, for me, 30* and lower for my truck. And all night.
You can get a heavy duty timer to plug into and have it start 3 hours before you need it. Now the above test was at a pretty warm temp, I haven't seen anyone post from a lower starting temp. (Too cold to go out and write down temps, which, I don't blame them!!!)
(to have clearer windshield you must have the heater set to defrost and temp control on high)
My truck likes to be warm. So, for me, 30* and lower for my truck. And all night.
You can get a heavy duty timer to plug into and have it start 3 hours before you need it. Now the above test was at a pretty warm temp, I haven't seen anyone post from a lower starting temp. (Too cold to go out and write down temps, which, I don't blame them!!!)
Can you get more info on Oil temp when plug block heater? I know it doesn't heat but I am curious how coolant 80oF in 1 hour affect oil temp. My 7.3L doesn't had coolant temp available on AE scanner.
I'm hitting easy street
Joined: Nov 2009
Posts: 6,395
Likes: 27
From: Central Oregon
I like getting the oil heated up. I think the injectors like warm oil.
Posting Guru
Joined: Jan 2008
Posts: 2,408
Likes: 0
From: Trenton, MI
All I can give you is what I posted. I wasn't looking at oil temps until hour 3. I don't believe the block has had much time to heat the oil in 1 hour. The warmer the block got, the faster the oil heated up.
I like getting the oil heated up. I think the injectors like warm oil.
I like getting the oil heated up. I think the injectors like warm oil.
I know my 7.3L hate winter. It struggle start. If oil is 47oF or less it HARD. If oil is 80oF in winter it crank and run like nothing happened that you notice when cold start with 20oF.
I wonder if it worth add oil heater and not use block heater.
Posting Guru
Joined: Jan 2008
Posts: 2,408
Likes: 0
From: Trenton, MI
HAHA my friend did that for whole winter 2 years ago on foreclosed house. Let say Bank were mad and had electric company and water city come to shut down it.
Tuned
Joined: Oct 2011
Posts: 269
Likes: 0
From: Albuquerque, NM
That's interesting, and something I never really considered. How much electricity does the block heater draw? I didn't think it would draw enough to really make much difference in the electric bill.
Posting Guru
Joined: Jan 2008
Posts: 2,408
Likes: 0
From: Trenton, MI
I forgot one post I think here. He claim it cost $15 dollars MORE a months in electric if plug overnight. Those block heater on 7.3L powerstroke I heard 1000 or 1500 watts.