View Full Version : Can an engine run too cold?

07-23-2004, 02:09 PM
I have a 67 chevy C-10 with a 72 350 4-bolt main and I was having overheating problems so I figured out it was rad since everything else is new. I was running in city traffic on scorching hot day upwards of 225 degrees (not moving) with 185 thermostat. I bought an aluminum rad and dropped stat to 160. Problem solved I am running steady 155-160 on really hot day sitting in alot of traffic it went to 180. Can it be bad to run at a low temp like 155-160? Someone told me it is. If so I was going to put the higher 185 stat back in.

07-23-2004, 02:12 PM

07-23-2004, 02:19 PM
When an engine runs cold so does its lubricating oil, which means more potential for moisture and acid to form in its oil. At higher temps (both oil and engine) harmful deposits are boiled off. This prevents the slow destruction of bearing material and shortened engine life.
When an engine runs too cold, the fuel economy goes down, often way down. A decrease of 6 to 10 miles per gallon isn’t unusual and as fuel consumption increases so does wear. Wear increases because of two factors. First, the cold engine doesn’t heat the oil sufficiently and harmful deposits, moisture, and acid accumulate rapidly, then eat away at the inside of your engine. Thats why flaming exhausts are bad ideas, your liturally pouring gas down your cylinder walls...Yea but its fun anyway...

07-23-2004, 02:29 PM
Install a 190 deg. thermo and you should be in great shape.--TV

Unkl Ian
07-23-2004, 02:49 PM
As well as the correct answers above,there is one more reason.

There is actually more friction in a motor that is 20 degrees too cool,
than one which is 20 degrees too hot.

The oil needs to get above 210F as soon as possible,a 190 thermostat should do the trick.

07-23-2004, 03:46 PM
the theroy is that the hottest you can get your engine to run without overheating is the most efficiant it will run.
I think the new corvettes have 235o thermostates in them!!

07-23-2004, 03:47 PM
The 160 degree thermostat holds the water in the block until it reaches 160 degrees and then it lets it go... the temp drops to 155, thermostat closes, and then the cycle starts all over again.

Basically, the radiator is doing its job very well.

So put a 180 or 195 thermostat in the thing and be done with it... If it pukes fluid after you shut it off, check the cap pressure, make sure it is not defective. This is assuming that you are running a recovery tank, which you should be running.

With the 180 degree thermostat, your temp should stay at or under 180 the majority of the time. If the outside temp is 110 degrees... and you're in standing traffic for long periods of time, don't be alarmed if the temp rises 10 or 20 degrees... 210... 215... but if it keeps climbing and you can't get it under control, pull of and get some air flowing.

I doubt you'll have this problem though, it sounds like you got a good radiator.


07-23-2004, 06:25 PM
Well, overheating could also be attributed to water not staying in the radiator long enough as well as staying in the motor too long. If the thermostat is too cold, (or you have no t-stat at all) the water pump might be running it through too fast for the radiator to have a chance to cool it all the way down, so the motor takes it back in hot, and it keeps going like this until it snowballs and the radiator heat-soaks and you're screwed. A high t-stat (190+), combined with a radiator/fan/shroud big enough to pull it back down in a hurry will keep you and your motor happy for a long time.

Unkl Ian
07-23-2004, 06:35 PM
the theroy is that the hottest you can get your engine to run without overheating is the most efficiant it will run.

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Oil runs about 20+ degrees hotter than the water,
and Petroleum oil starts to break down above 250F.

Flat Ernie
07-23-2004, 08:58 PM
Petroleum oil starts to break down above 250F

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And when it does, it loses all of its lubricity (I think that's a word) & acts like water - in severe situations, you can get thermal runaway (not likely in an car - the engine will likely seize first)...

07-23-2004, 10:33 PM
Maybe ol Parafin based sig weigh oils broke down at 250o( or start to) But good muilti grade pennsyvania oils get get up in temp before they breakdown, 250o ain't hit to them.
If that was the case every car would have a oil cooler.
Look at a trans, they use the water in the rad to cool them down!!

07-23-2004, 10:50 PM
pennsyvania oils

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Don't those oils have parafin in them...
Like Quaker State>>>>>

Flat Ernie
07-24-2004, 04:02 AM
Don't those oils have parafin in them

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I'd never recommend "Quaker Cake" to anyone...

Hell, I prolly just called someone's baby ugly, but...

07-24-2004, 08:17 AM
They do have parafin in them, but they seem to have the right balance say between West coast oils & Middle east oils.
Don't under estimate penn oils,it's good shit.when I was in the Navy we ran waukesua V-12 diesels in a Minesweeper & That was the one reason they ran Penn oils,cause they where the all around best of the best.
Of coarse you can buy Middle easy oils They Need more AK-47's over there!!lol.Just kidding, couldn't resist waving the flag

Flat Ernie
07-24-2004, 10:31 AM
Most of the non-car folks know me as a gearhead, so when they ask for oil I have two recommendations for "off the shelf" buying:


If they don't want to spend the $$ for Mobil-1 & can't find Kendall, I recommend Havoline or Motorcraft (repackaged Havoline).

Never have liked Quaker Cake - although they were the last ones to get rid of the old cardboard cans - gotta like that!

07-24-2004, 11:02 AM
Actually I'm not a fan of Quaker state either.But I'm a BIG fan of Pennzoil.They just don't have the "Madison ave" push tht quaker state has.