Engine Block Heaters -- When to use them? Any risk of damaging your engine?

[WhipperSnapper]

I just had an engine block heater installed in my car since I'm now living in a place where it gets very cold.

Should I keep my car plugged in all of the time or should I just plug it in an hour before I'm planning to go out?

Should I keep it plugged in all the time to reduce the risk of freezing coolant cracking my engine block?

Can I do any sort of damage by keeping it plugged in continuously? Is it possible that it could heat up the coolant resulting in evaporation and eventually too little coolant?

 

[RedRooster]

Below about -20C I just leave it plugged in all the time. Warmer than that I just use an outdoor timer to turn on about 3 or 4 hours before I go to work. You should plug it in a couple hours at least for the best effect.
And make sure your coolant is good for -40C, no worries at all if it is. Unless you have one of those fancy recirculating warmers that actually attach to your rad hose and pump it through continuously.

 

[WhipperSnapper]

Thanks for the advice. I like the outdoor timer idea.

 

[RU482]

I've been thinking of adding a block heater, from the perspective that my car's fuel economy really tanks this time of year, so I'm wondering if starting out with a warm engine would reduce the amount of time the car takes to "warm up" in the morning, and thus improve fuel economy (possibly more than paying for the electricity and cost of the heater)

thoughts?

 

[Rezist]

You probably won't get better fuel economy but your starter and engine will last alot longer, your engine will also "warm up" faster but your talking the difference of only a few minutes.

 

[PsiStar]

The only damage I can think of is driving away with the thing still plugged in.

 

[mmntech]

They'd be great if they actually warmed up the coolant enough where you actually got heat right away. I doubt it works that way though. People only really use them in very cold places. We're talking way north of 40.

You're better off putting a lighter weight oil in your engine during the cold months. Helps with cold weather starting because the normal stuff gets thick like molasses.

 

[herm0016]

how cold is "very cold"? I need one in my work trucks because they are diesel. I have not needed one in my personal truck (gas) but would use one if power was easily available when the temps were below single digits.

 

[3chordcharlie]

how cold is "very cold"? I need one in my work trucks because they are diesel. I have not needed one in my personal truck (gas) but would use one if power was easily available when the temps were below single digits.

Diesels will see a benefit from a block heater at around 30F (0C); they're generally hard-starting to begin with, and you can really save excessive use on the glow plugs.

Gas motors tend to be 100% fine down to about 10F (-10C); if you get a block heater timer, it will probably have a temperature based setting, and likely trigger at this temperature. The only trouble I've ever had starting a gas (car) motor was an old carbureted one where the choke stuck starting around -20F (-30C) (that was a cold f'ing winter).

Make sure you unplug the block heater BEFORE you start the engine; when the coolant starts pumping, there can be an air gap over the heater element, which may decide to go BOOM.

 

[exar333]

Diesels will see a benefit from a block heater at around 30F (0C); they're generally hard-starting to begin with, and you can really save excessive use on the glow plugs.

Gas motors tend to be 100% fine down to about 10F (-10C); if you get a block heater timer, it will probably have a temperature based setting, and likely trigger at this temperature. The only trouble I've ever had starting a gas (car) motor was an old carbureted one where the choke stuck starting around -20F (-30C) (that was a cold f'ing winter).

Make sure you unplug the block heater BEFORE you start the engine; when the coolant starts pumping, there can be an air gap over the heater element, which may decide to go BOOM.

This is pretty accurate. Unfortunately, it gets much colder than this around here (MN) so the block heater is very useful. My rule of thumb was to plug my car in when the temp was getting close to 0F and the car had to sit outside for >10-12 hours. On those days that were -5F or colder, having the block heater made a world of difference in not only starting your car, but you could start it and drive it much better without having to warm it up.