about oil temperature

[Ahke]

Hi guys,

I wouuld like to know the effect of motor oil in the ability to resist engine temperature rising. Which item in an oil analysis data should I look for this purpose? TKS

 

[Ahke]

moreover....
Is there something called "evaporation data" on a oil analysis report? thank you.

 

[Voltmaster]

Theoretically the oil shouldnt get to that level under normal driving condition.... most of the engine cooling is done through the cooling system and radiator.


However oil is sprayed around the pistol taking a lots of heat off it.So some small amount will get too hurt and burn or evaporate, thats is what you looking for, so look at that the tests done in high temps in the reports.

As far as I know no one really does these tests for sample , how the oil does in high temps shows how much it would evaporate so look at those indications.

 

[SteveSRT8]

Volatility is a regular spec for new oils. This may be what you seek.

Note that few engines actually spray oil at the undersides of the pistons. It is typically found only on supercharged/turbo'd and/or very high performance applications.

 

[95busa]

Lots of motorcycles use piston squirters....fwiw

 

[Ahke]

Thank you very much for these useful info.

 

[Ahke]

Yeah, my car is tubocharged. I think the volatility is what I am looking for. Thank you very much.

 

[bepperb]

NOACK is a common oil spec, it is the percentage of oil that burns off during a controlled experiment. I believe it's run at 250 degrees, hotter than most oils would run.

Oil can mitigate hot spots (as it is used as a piston squirter) but as the system is often completely contained within the engine it shouldn't have any ability to dissipate heat from the system as a whole. An oil cooler or an oil to coolant heat exchanger would change this, obviously.

 

[A_Harman]

The best indicator of volatility that you can find on an oil data sheet is NOACK. A lower number is better, meaning that less oil will evaporate at high temperature.

 

[Quattro Pete]

Originally Posted By: Ahke
Hi guys,

I wouuld like to know the effect of motor oil in the ability to resist engine temperature rising.

Generally, the lower the viscosity of the oil, the lower the operating temps that you're going to experience. Thicker oil causes more friction and results in extra heat.

 

[KCJeep]

I don't believe that's right. Thicker oil is not able to dissapate heat as quickly, so temps run a bit higher, it's not due to extra friction.

 

[Ahke]

wow;I didn't think of the friction effect. However, isn't there a contradition since higher viscosity always have lower volatility?

 

[Ahke]

Thank you for the concept about the dissipating heat in a closed system.

 

[Ahke]

Does that mean thicker oil build up more temps than thinner one? or the engine temp should be the same with the same cooling system?

 

[Quattro Pete]

Originally Posted By: KCJeep
I don't believe that's right. Thicker oil is not able to dissapate heat as quickly, so temps run a bit higher, it's not due to extra friction.

Let's put it this way: the engine has to work harder to push thick oil around. You are getting worse MPG because instead of delivering power to the wheels, some of it is turned to heat inside the engine.

 

[CATERHAM]

Originally Posted By: KCJeep
I don't believe that's right. Thicker oil is not able to dissapate heat as quickly, so temps run a bit higher, it's not due to extra friction.

Correct but the effect is subtle unless the oil is so thick that the oil pump goes into by-pass mode further reducing the oil flow through the engine and this would be most noticeable under maximum load conditions.
In really it's a non issue if the oil viscosity is chosen correctly following the "as thin as possible, thick as necessary rule".

Regarding evaporative losses of motor oil. Generally it is not an issue unless the oil temp's are often well above 100C. In which case choosing a higher quality (and more expensive) oil with a lower NOACK percentage (as has already been mentioned) is the solution.

 

[mechtech2]

Originally Posted By: Quattro Pete
Originally Posted By: Ahke
Hi guys,

I wouuld like to know the effect of motor oil in the ability to resist engine temperature rising.

Generally, the lower the viscosity of the oil, the lower the operating temps that you're going to experience. Thicker oil causes more friction and results in extra heat.


This^^. Also thicker oil coats parts and does not transmit heat as well away from them.

 

[boxcartommie22]

i look at it this way5w30 vis @212f.is 10.7 that is still very thin oil at operating temp...right?

 

[CATERHAM]

Originally Posted By: boxcartommie22
i look at it this way5w30 vis @212f.is 10.7 that is still very thin oil at operating temp...right?

Compared to a 20wt oil it's very thick but it still depends what the actual "operating temp's" are. That KV100 is just a spec'.
If the operating temp's are 80C which is not unusual yes it's very thick but if the oil temp's got to 120C yes I'd say it's pretty thin but likely still not too thin.

 

[skyship]

Some of you have got rather mixed up about the relationship between viscosity, temperature and friction.
Firstly the lower the viscosity the lower the oil temperature, so a 30 grade oil will result in a lower operating temperature than a 40. That occurs because the thinner oil is pumped around the engine faster than the thicker oil.
Obviously some power is lost pumping thicker oil around an engine, so the fuel consumption increases by a few percent if you change from using a 30 to a 40 grade oil.
In general terms if you ignore the effect of local hot spots around the pistons at very high power settings, the higher the upper viscosity range the better, so some engines do produce slightly better wear figures when hot if a 40 rather than a 30 grade oil is used.
Most wear results from cold starts so the lower W rating is much more important than the upper rating for a multigrade engine oil.
The oil used in most F1 race engines is only SAE 10 to 15, so is rather light in comparison to normal engine oils, BUT the power loss reduction from using thin oils is very important as is the faster oil flow that can dissapate heat from the oil cooler faster.