Overheating engine... run Thin or Thick oil?

[veryHeavy]

My ancient 1 liter/3 cylinder car likes to overheat when climbing steep mountain grades during California summers. 5W20 is the recommended oil, but I switched to 5W40 for more high temperature protection.

Thinner or Thicker?
Which is better for a very hot engine?

 

[Kuato]

Ancient and overheating tells me your cooling system isn't what it needs to be. Radiator probably has some scale buildup inside that is reducing cooling capability. If that's up to snuff...well...oil is not going to make enough of a difference in cooling so thicker would be better. I'd be concerned about your head gasket.

 

[bioburner]

Auxiliary fan coolers? Finned oil cooler. I am looking at one for the Transit $25

 

[bioburner]

Originally Posted By: Kuato
Ancient and overheating tells me your cooling system isn't what it needs to be. Radiator probably has some scale buildup inside that is reducing cooling capability. If that's up to snuff...well...oil is not going to make enough of a difference in cooling so thicker would be better. I'd be concerned about your head gasket.

The old 3 hole doesn't have the guts to do any elevation my guess. Probably a carb job too.

 

[Chris142]

It will blow a head gasket before needing a thicker oil.

 

[MolaKule]

Thicker oil means more heat energy going into the oil and raising overall temps.

Clean out the radiator.

 

[69GTX]

I'd add a little bit more margin and improved heat transfer by running a 60-40 to 70-30 water/coolant mix in the summer. I ran 90-10 during the summers on one of my cars that just would never run cool no matter what I tried. I did everything externally possible except rebuild the engine and/or clean out all internal passages....and the radiator was new too.

The thinner or OEM recommended oil will transfer the heat more quickly. The question is, can you keep oil temp away from 275-300+ deg F where problems could start occurring and your oil really thins out? You may have to clean out your cooling passages as well as the radiator. Ensure your radiator air flow is at optimum...increase it if you can.

 

[zeng]

This is where thicker oil with higher margin of safety than thinner oils comes in .............. though underlining coolant temperature phenomenon is to be managed.

Edit:
a typical 5W40 at 120*C has similar operating viscosity protection level as a 5W20 at 100*C.
20*C is huge margin btw!
I would ignore indiscernable difference in heat transfer coefficient and churning heat loss, more so at operating temperatures.

 

[Ducked]

My ancient (1986) 1 liter/3 cylinder car is OK SO FAR in Taiwan summers (Surprised there are any in the US. Don't you get into bar fights with cowboys?) but I use 40 mixed with 15/40, which perhaps would give me a bit of reserve viscosity if it overheated. 10W30 is the recommended oil.

Head gaskets are apparently especially vulnerable on these. You should probably try and clean out the cooling system.

Half-assed improvisations might include removing the thermostat, if that isn't too difficult, and/or maybe an emergency water spray for your radiator.

 

[DoubleWasp]

Originally Posted By: veryHeavy
My ancient 1 liter/3 cylinder car likes to overheat when climbing steep mountain grades during California summers. 5W20 is the recommended oil, but I switched to 5W40 for more high temperature protection.

Thinner or Thicker?
Which is better for a very hot engine?



You need to solve your cooling problem if possible.

There is always the possibility that even in tip-top shape, that car was always going to do the same thing.

If that is the case, consider a better radiator.

What's the year, make, and model anyway?

 

[FCD]

If your car is overheating, the problem you ought to be solving is not the oil but the cooling system and figure out why it's overheating and fix it

 

[bmwjohn]

we are guessing Suzuki Swift or GEO Metro or similar, but there is other stuff.....what do you have? Do you have a sealed cooling system? If not consider the little $10 kits from AZ that add a little plastic tank and a gasket for the thermostat. Of course a bigger or recored radiator wouldn't hurt anything.

 

[FZ1]

Thinner is cooler. Does running 1 gear lower on the hills help?

 

[Shannow]

While a thicker oil will generate more heat due to internal friction, it will typically always have a higher minimum oil thickness than a thinner in any sort of reasonable engine oil viscosity.

It won't MAKE it overheat, MAY provide more reserve, but overheating is not a proposition that allows long term operation on any oil.

You don't have any issues in Utah and Nevada by the sounds of it.

 

[Pop_Rivit]

Originally Posted By: veryHeavy
My ancient 1 liter/3 cylinder car likes to overheat when climbing steep mountain grades during California summers. 5W20 is the recommended oil, but I switched to 5W40 for more high temperature protection.

Thinner or Thicker?
Which is better for a very hot engine?



Why not drive the Challenger you pretend to have or the Honda you pretend to have?

 

[kc8adu]

water pump impeller is rotted away.
or head gasket leaking into coolant making bubbles in the system.
soon to get worse by running it hot.

 

[Shannow]

Originally Posted By: Pop_Rivit
Originally Posted By: veryHeavy
My ancient 1 liter/3 cylinder car likes to overheat when climbing steep mountain grades during California summers. 5W20 is the recommended oil, but I switched to 5W40 for more high temperature protection.

Thinner or Thicker?
Which is better for a very hot engine?



Why not drive the Challenger you pretend to have or the Honda you pretend to have?


There was a pretty FarFetched poster a while ago who would, in these situations claim that he was only posting hypotheticals for encouraging discussion.

Those other cars seem like more fun to drive halfway across a country to hillclimb in (now winter) California.

 

[Nickdfresh]

Originally Posted By: Pop_Rivit
Originally Posted By: veryHeavy
My ancient 1 liter/3 cylinder car likes to overheat when climbing steep mountain grades during California summers. 5W20 is the recommended oil, but I switched to 5W40 for more high temperature protection.

Thinner or Thicker?
Which is better for a very hot engine?



Why not drive the Challenger you pretend to have or the Honda you pretend to have?


Good catch! LOL

And OP, buy a new radiator. Or do have have bad "parts counter experiences at dealerships?"

 

[cmhj]

d

 

[FCD]

Originally Posted By: Shannow
While a thicker oil will generate more heat due to internal friction, it will typically always have a higher minimum oil thickness than a thinner in any sort of reasonable engine oil viscosity.

It won't MAKE it overheat, MAY provide more reserve, but overheating is not a proposition that allows long term operation on any oil.

You don't have any issues in Utah and Nevada by the sounds of it.

+1 While thinner oils may create less heat through friction, it is still better to run a thicker oil if you have an engine that is running hotter than usual especially at track days and thing like that, te new Corvette Z05 recomends 5W-30 for normal driving , but Mobil 1 15W-50 when being used on the track and being driven hard.