Why don't they use oil instead of water to cool engines?

The_Unbeliever

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Was just wondering why they don't use oil instead of water to cool down engines...

Call it a #RandomThought
 

Pox

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Thermal conductivity of water is higher than oil, which means water can absorb and release heat a lot faster than oil.
So if you use water you can use smaller radiators.
 

froot

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Water cools down quicker than oil, so if you were to use oil you'd have a car running hotter than what it would be if you ran it with water.
Ok fine, I cheated. I asked Ook-brother :D
 

Compton_effect

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Viscosity, conductivity, simplicity and the big one - Cost.
Water cools faster, and a water cooled system is simpler and cheaper than a oil based one.
 

Sinbad

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Was just wondering why they don't use oil instead of water to cool down engines...

Call it a #RandomThought
Oil does in fact play a major cooling role in the engine - it's used to cool down pistons and other hotspots. But yes, water is the major player in removing heat from the engine as a whole. Except in air-cooled motors of course
 

SirFooK'nG

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Imagine all oil spills on the roads at every accident....

EDIT: And fires from oil combustion on exhaust manifolds in an accident... Also oil retains heat (hence oil heaters) better than water. So cooling would definitely be inefficient!
 
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Keegan

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Thermal conductivity of water is higher than oil, which means water can absorb and release heat a lot faster than oil.
So if you use water you can use smaller radiators.
^ This.
 

HapticSimian

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They do use oil to cool down engines. What makes you think they don't?
It's part of a greater whole, sure, but oil is used more to a) counter friction, and b) carry heat to where it can be dissipated by air or water cooling. But that's really over-analysing an Ook[-]Fart[/-]Thought.
 

Budza

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Some motorbikes are oil cooled- engine oil is passed through a small radiator.

http://en.wikipedia.org/wiki/Oil_cooling :

Advantages
Oil has a higher boiling point than water, so it can be used to cool items at a temperature of 100°C or higher. However, pressurised water-cooling may also exceed 100°C.
Oil is an electrical insulator, thus it can be used inside of or in direct contact with electrical components.
Oil is already used as a lubricant, therefore it may serve in a double use arrangement.

Disadvantages
Coolant oil may be limited to cooling objects under approximately 200°C - 300°C.
Parts are hard to take out and put in after the oil is put in.
Water is almost universally available in case coolant needs to be added to the system, but oil is not.
Unlike water, oil may be flammable.
 

Rocket-Boy

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Its a similar situation to cooling in PC's where copper conducts heat better but aluminium dissipates it faster.
Oil is a better conductor of heat than water is but it takes longer to cool down than water does.
 

SauRoNZA

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As was said already the main reason there is oil in the engine in the first place is to reduce friction which directly accounts for reducing heat.

Air cooling doesn't actually cool the engine, but cools the oil going through the engine instead. Ever heard of an oil cooler? Those are pretty much found on air-cooled engines only.


It's simply not as efficient as liquid cooling and as you can imagine is rather inconsistent depending on the weather.
 

ost

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^^ What they said

But also if your head gasket blows you won't see the indication of oil mixing in your water
 

Paul_S

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They do use oil to cool down engines. What makes you think they don't?
Motor vehicles with engine oil coolers use the coolers mainly to keep the temperature of the oil down (to prevent ruining the oil) and not as a means of primary cooling. You will almost always find that these engines use air or water for primary cooling.
There may be rare exceptions although I am not aware of any in a motor vehicle.
Even the ancient aircooled VW Beetle engines have an oil cooler to keep the oil temp down.
 
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Paul_S

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Air cooling doesn't actually cool the engine, but cools the oil going through the engine instead.
Nonsense. Why do aircooled engines have powerful fans blowing on fins on the cylinder heads then?
Most lawn mowers are air cooled and the majority don't have an oil cooler.

Ever heard of an oil cooler? Those are pretty much found on air-cooled engines only.
Nonsense again.
You'll find oil coolers on plenty of water cooled engines.
Ford Essex V6, Mazda RX7, Mercedes Vito ...
And I'm not confusing it with a transmission oil cooler.
 
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