Before and after 150 watt oil pan heater. Guess?

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Originally Posted By: Jetronic
Originally Posted By: JHZR2
Figure the specific heat of oil is 2kJ/kg*K

Figure 6 quarts of oil weighs 4 kg.

Figure the heater has to heat the ambient (poor insulation and no guard heater), and the metal, so efficacy is maybe 30ish%.

So 50W going in means 50J/sec.

Every 20 sec maybe 1kJ.


Need 8+ kJ to raise 1 Kelvin.

So 1K every 160 secs.

So after 1 hr around 20K, which is a factor of 9/5 so 38ishF? Seems about high but the engine thermal mass and losses are a total swag.

As it warms, delta T with ambient will increase so losses will go up until some steady state is obtained.

I'm scratching this at breakfast counter in a restaurant do someone can check my conversion and math.


6 quarts of oil is closer to 5 kg, so probably 20% less heat rise per hour than you calculations... didn't bother looking up te specific heat of oil (depends if it's PAO, gr V or dino anyway) but I'm sure the specific heat of the oil pan itself is 3 times higher than the oil it contains and could be another 3-5 kg...


I have to think that the difference between pao, ester, and hydro cracked lubes is minimal in terms of specifi heat. First, second decimal place? Could be wrong.

While the heater will certainly have to heat the pan and will dissipate in the x and y directions, the length scale in z is much shorter and should facilitate heat transfer preferentially into the oil. This is doubly so given that heat spread in c and y will continually shed energy in z as the oil further and further out is cold. Conduction all the way to the block I'd argue is viable, but secondary until heat transfer in z along the whole wetted surface drops below in plane conductivity. The rates do probably differ by an order of magnitude though...
 
Originally Posted By: Gasbuggy
I checked this morning and I was down to 14 degrees for oil temp. I turned the heater on, after 1 hour my oil temp was reading 49 degrees and the ambient temperature was unchanged. Looking forward to what hour 2 brings.



By hour 2 I was at 60 degrees. Hour 3, 62 degrees. Hour 4, 62 degrees.

I did not let it idle, I began driving. My oil temp receded to 60 and held that temperature for a couple miles before moving up as usual. By the time I reached my usual destination 11 miles away my oil temp was about 30 degrees warmer than normal. 177 vs the usual 147ish.
 
I would put a better filter on there i had the same problem with the pure one filters a few years back before the tearing issues. I wrote about it here on Bitog. Just curious was it the older filter or the newer ones with the super small oil holes? Also do you really need an oil pan heater in P.A.? I would worry about a fire but thats just me.
 
Originally Posted By: Gasbuggy
Originally Posted By: Gasbuggy
I checked this morning and I was down to 14 degrees for oil temp. I turned the heater on, after 1 hour my oil temp was reading 49 degrees and the ambient temperature was unchanged. Looking forward to what hour 2 brings.



By hour 2 I was at 60 degrees. Hour 3, 62 degrees. Hour 4, 62 degrees.

I did not let it idle, I began driving. My oil temp receded to 60 and held that temperature for a couple miles before moving up as usual. By the time I reached my usual destination 11 miles away my oil temp was about 30 degrees warmer than normal. 177 vs the usual 147ish.


Another test, I plugged the heater in when I got home today. The oil temp was 183 starting out. Ambient temp was 24 to 18. After 8 hours my oil temp was 87 degrees and my coolant temp was 39. The oil temp drops faster than the coolant temp (sensor location). I would say at that after 8 hours the heater kept the oil 55 degrees warmer than it would be otherwise. I pulled the dipstick and the oil on it was nice and warm. I unplugged it because the car will not move tomorrow.

All in all I am happy with this pan heater. I would put one on my transmission and differential if I could snap my fingers and have it done. I am unsure to what extent this will reduce cold start wear but I am glad to begin a trip with oil that is much closer to a comfortable operating temperature since I don't do warm ups and remote start with stick shift is an accident waiting to happen.
 
Originally Posted By: crazyoildude
I would put a better filter on there i had the same problem with the pure one filters a few years back before the tearing issues. I wrote about it here on Bitog. Just curious was it the older filter or the newer ones with the super small oil holes? Also do you really need an oil pan heater in P.A.? I would worry about a fire but thats just me.



Do I need one in PA, that is relative. If given the choice I would rather start with 60 degree oil than 14 degree oil, and now I have that choice. Sometimes I work in New Hampshire and that factored into my decision too. The warmer the better. I don't see fire as a concern with the location and low wattage/temperature.


I installed that filter before I was aware of all the issues. I bought it from a newer, busy, Advance Auto in October so probably is a newer style. I had not looked at the filter section of this site in years. I was shocked to see Fram and Purolator had swapped places.
 
Originally Posted By: DoubleWasp
Shouldn't the bypass take care of any cold oil flow issues?


It should, and I'm sure it is. The ECU has a very sensitive requirement and I am running a thicker oil in negative temperatures. I can understand that the 40wt is not moving as quickly as would normally be expected. Most vehicles don't have something like this available to display, it is probably the equivalent of a car that starts up on a bitter cold morning and the little oil light stays on for a second longer than usual.
 
The one I use on my semi truck is a 500w probe type that replaced a plug in the side of the panned runs about 10" into the pan submerged in the oil. Does not affect the normal drain plug. I have never done any temp measurements on it, but I I have touched the band and it is warm to the touch, so best guess would be 80-90F. I know the truck starts much better with using it in cold weather. Probably a little more efficient that the stick on versions in that the entire heating element is inside the pan and bathed in oil.
 
This is a pretty easy question to solve.

Whats the Capacity?

Q = Mass *Cp* (Delta T)

CP is specific heat

Q is in joules. 150watts is 150 j/s so multiply by 60 for 1 min.etc.

Input a start temp and solve for the end temp. easy.

So for 5 quarts of oil and one hour at 0C

540000 jouls = 4082 g * 1.8 J/g*c * (x-0)

so 66-73C but this is for a perfectly insulated system, obv oil pan isn't. lets say only half of 150 watts is going to cooling due to heat loss now you are at 33-36C

As oil heats up its Cp changes but only to around 2ish at 100C,
 
Last edited:
Originally Posted By: JHZR2
Figure the specific heat of oil is 2kJ/kg*K

Figure 6 quarts of oil weighs 4 kg.

Figure the heater has to heat the ambient (poor insulation and no guard heater), and the metal, so efficacy is maybe 30ish%.

So 50W going in means 50J/sec.

Every 20 sec maybe 1kJ.

Need 8+ kJ to raise 1 Kelvin.

So 1K every 160 secs.

So after 1 hr around 20K, which is a factor of 9/5 so 38ishF? Seems about high but the engine thermal mass and losses are a total swag.

As it warms, delta T with ambient will increase so losses will go up until some steady state is obtained.

I'm scratching this at breakfast counter in a restaurant do someone can check my conversion and math.


Here’s the same calculation with a bit different figures. The end result is the same, however.

- Specific heat of oil = 1.8 kJ/kg*K (Varies depending on the information source. Is temperature dependant)
- 6 quarts of oil = 5.7 liters = 4.8 kg (when using density = 0.85 kg/liter)
- 1/3 of the heating power goes to the oil = 1/3* 150W = 50W
=> 21 K/hour = 37 F/hour

The two tests gave:
1) 14F -> 49F in one hour. Delta = 35 F/hour
2) 23F -> 64F in one hour. Delta = 41 F/hour

So, the theory and reality seems to match quite nicely, when using 1/3 efficiency.
 
Below are the recommended wattages for different oil sump sizes and the respective temperatures calculated with the same equation as above.

Wolverine pad heaters:
- 125W: 3 – 6 quarts => 31 – 62 F/hour
- 250W: 5 – 13 quarts => 29 – 75 F/hour
- 500W: 13 – 27 quarts => 28 – 57 F/hour

Kat’s pad heaters:
- 100W: 2 - 5 quarts => 30 - 75 F/hour
- 150W: 5 – 8 quarts => 28 - 45 F/hour
- 250W: 8 – 20 quarts => 19 - 47 F/hour
- 500W: 20 – 35 quarts => 21 – 37 F/hour

As d00df00d already mentioned, you want to heat the oil not to fry it. So, the OP’s heater seems to be spot on.
 
Originally Posted By: finmile


As d00df00d already mentioned, you want to heat the oil not to fry it. So, the OP’s heater seems to be spot on.


It is very difficult to "fry" the oil with a properly sized heater. Heat rises up through the oil, heating all the oil, and the crankshaft and parts above as the heat rises. I had this discussion with the tech guy over at Wolverine heaters when he helped me size my Wolverine heaters. Anyone considering one should give them a call and ask. They'll explain the science behind it.
 
Ah ha, we forgot to consider the additional, rapid, heat transfer via the aluminum oil pan. The oil will remain cold in extreme cold temps in such a situation. 4 cylinder Aircraft engines with 250 watt heaters are just barely able to "crank" when it's 0 or below.
 
Originally Posted By: demarpaint
It is very difficult to "fry" the oil with a properly sized heater. Heat rises up through the oil, heating all the oil, and the crankshaft and parts above as the heat rises. I had this discussion with the tech guy over at Wolverine heaters when he helped me size my Wolverine heaters. Anyone considering one should give them a call and ask. They'll explain the science behind it.


Sure. A properly sized heater does nothing harm.

But I meant that if someone would go a bit crazy with the heater, for example 500W for 5 quarts sump, wouldn't there be a risk for too high surface temperatures on the oil pan (locally where the heater pad is)? And thus some adverse effects on the oil.
 
Silly me. I could have just used watt/quart.

Wolverine pad heaters:
- 125W: 3 – 6 quarts => 21 - 42 W/quart
- 250W: 5 – 13 quarts => 19 - 50 W/quart
- 500W: 13 – 27 quarts => 19 - 38 W/quart

Kat’s pad heaters:
- 100W: 2 - 5 quarts => 20 - 50 W/quart
- 150W: 5 – 8 quarts => 19 - 30 W/quart
- 250W: 8 – 20 quarts => 13 - 31 W/quart
- 500W: 20 – 35 quarts => 14 - 25 W/quart

=> It seems that one should never go above 50 watts per quart.
 
Originally Posted By: finmile
Originally Posted By: demarpaint
It is very difficult to "fry" the oil with a properly sized heater. Heat rises up through the oil, heating all the oil, and the crankshaft and parts above as the heat rises. I had this discussion with the tech guy over at Wolverine heaters when he helped me size my Wolverine heaters. Anyone considering one should give them a call and ask. They'll explain the science behind it.


Sure. A properly sized heater does nothing harm.

But I meant that if someone would go a bit crazy with the heater, for example 500W for 5 quarts sump, wouldn't there be a risk for too high surface temperatures on the oil pan (locally where the heater pad is)? And thus some adverse effects on the oil.


That's true for just about everything in life.
wink.gif
 
Originally Posted By: finmile
But I meant that if someone would go a bit crazy with the heater, for example 500W for 5 quarts sump, wouldn't there be a risk for too high surface temperatures on the oil pan (locally where the heater pad is)? And thus some adverse effects on the oil.

I don't think 500 watts would be too high for five quarts, at least in a lot of winter conditions we see here. I still keep forgetting to check the size of my heater. But, of course, as you mentioned, don't go crazy. I wouldn't think it too brilliant to be using a 500 watt heater in my G37 when it's +5 C out just to make it easier for me to use a monograde SAE 40 or something similarly bizarre. That would simply be inventing problems for oneself to solve.
 
Next car
Originally Posted By: Cujet
Ah ha, we forgot to consider the additional, rapid, heat transfer via the aluminum oil pan. The oil will remain cold in extreme cold temps in such a situation. 4 cylinder Aircraft engines with 250 watt heaters are just barely able to "crank" when it's 0 or below.



Good thinking on the aluminum pan.
 
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