My completely un-expert opinion is that is rated for ~250watts -- or about the same as putting two or three 100watt light bulbs underneath it all night. I can't imagine thats going to do damage, given your outside temperatures. If it was rated 1200+ watts, then I'd probably be more worried about too much heat.


Can you grab a friend's IR temp gun for a reading? That would put your mind at ease.



PS please report back from time to time about how the pad is holding up -- the pad sounds like a good idea for those that need it.

I have used these same pads (or very similar) on larger engines without any issues.

First point is to not trust your temperature gauge, it isn't very accurate. It has three positions, essentially, according to the buffer and programming built into it. Left is cold, right is too hot, and anywhere remotely close to the right temperature results in straight up. Analyzing it beyond those three conditions is fraught with risk.

You can't leave it on too long. It can't boil the oil. Once you determine how long it takes to reach equilibrium, however, any more time is just wasting electricity. Move it up an hour or two and see if it makes a difference. It shouldn't take any more than 3 or 4 hours IMO.

You can't warp the pan. You may contact the splash guard insulation or something else that doesn't like heat, but the pan is fine. Again, IMO.

If you have an oil immersion heater, you can get coking of the oil on the element, not good. Given how these silicon pads mount, they are very safe.

To put it in perspective, my four cylinder Volvo block heater was about 500 or 600 watts, mounted in the water jacket. It took 2 hours to get to equilibrium in Edmonton winters. I had one vehicle with a 1200 watt block heater, again, in the water jacket. It was hot in an hour, it was like plugging in a kettle (1500 watts).

You mention your battery. Are you using a battery blanket? A 50 watt blanket from Canadian Tire will make it turn over much more reliably. That does not need to be plugged in as long. We always used automatic timers.

If the interior of the vehicle feels like a block of ice (and it will) then get an interior car heater.

We would mount multiple heaters (jacket water, oil pan, battery blanket, interior) and run them all to a common power bar, on a timer. When I left in the morning I would unplug, and plug in my wife's vehicle so that it was ready an hour later for the school run.

Haven't used a plug in since 1990, but remember the drill very well.

Thanks JCL!

You have provided me with some incredibly useful and to the point information.

I have considered wrapping or covering the battery area under the spare with some sort of suitable (i.e. fire/chemical resistant) insulating material. I have also seen some of those interior heaters kicking around at Canadian Tire.

Good post JCL.

Yea my pops just read this threat as well. He said you have nothing to worry about.

The wattage on that pad is really not that high, and it is not even in the block. I would give it a few more hours run time to get it toastier.

There is no advantage to insulation around the battery because there is no heat there. Get a battery blanket. At -30 a battery has a small percentage of the power and reserve it has a normal temperatures. A 50 watt blanket really helps and they are cheap

" Specifications: CP 512 Model : 3.5 X 5.125 X .075 inches.

The pad just barely fit onto the oil pan, there is a small amount of pad, <1cm on the corner, that does not have any contact with the metal pan (which is not recommended.) "


You mentioned about "<1cm on the corner, that does not have any contact with the metal pan " i am wondering the pad is too long or too wide? as plan to install one too?

ThANks,

Too wide.

The aluminum pan conducts heat well. Not just to the oil but also outward to the rest of the block. 250 Watts is not that bad considering you have convective losses (that means heat lost to the air around the pan). I'm a heat transfer guy. Now if you were to take away the convective loss (i.e. be in space ha-ha) 250 W would be quite alot. I bet your oil isn't even getting to 35-40C. Perhaps you could find a way to install a thermocouple or use an IR camera.

One other thing you could have done was installed a thermostat in series to the heater. what that would mean is one of the two leads would have a open/close function when you reach a certain threshold temp. Mcmastercarr might have one. If you had it open at say 40C, you wouldn't have to worry with warping. The heater would just cycle off and on all night. I still think it wouldn't be too warm. I could do a computation. One thing though, how hard does the wind blow? That makes a big heat loss.