Engine Runs Cooler with Syns?

[HBCALI]

Can an engine oil claim to reduce vehicle operating temperature? I thought that was a result of the cooling system. For example, will my engine run "cooler" with synthetics (let's say Mobil 1) when compared to conventional?

Seems like a vague question, but in a hot climate, anything helps. Thanks.

 

[Quest]

Urban myth.

Also another typical housewifey's tale out on the public all the time:

(*example*):
poster: my car calls for 5W20 or 5W30 but since I live in houston, Tx or Florida, should I worry about oil not able to handle the Tx or Florida heat and thus go with 10W40?

Answer: you guess right (I'd rather go with 5W20/5W30, or whatever factory spec'ed for that particular vehicle engine design) than deviating from it (and play scientist by myself).

Q.

 

[Boomer]

Since the thermostat controls the temperature of the coolant, the engine temp will be the same. Now, it is possible that a syn may result in less friction and therefore less frictional heat generated so that the cooling system is dealing with less heat that it must dispose of but I would think that it would not be a large amount. If it were true, you would see it as an increase in gas mileage.

 

[440Magnum]

Originally Posted By: HBCALI
Can an engine oil claim to reduce vehicle operating temperature?


Absolutely not.

Now if one oil produces more friction, it does indeed contribute a little bit of heat to the engine more than what another oil might.. BUT!!! That difference is TINY compared to the total heat load of the engine. It would be like lighting a match in the boiler room of the USS Missouri while she was running at flank speed. Would it make the room hotter? Well, on some sub-atomic scale maybe so, but the thousands of gallons of fuel oil per hour burning next to the lit match would kinda tend to dominate how hot the room is.

 

[cmf]

Originally Posted By: Boomer
Since the thermostat controls the temperature of the coolant, the engine temp will be the same. Now, it is possible that a syn may result in less friction and therefore less frictional heat generated so that the cooling system is dealing with less heat that it must dispose of but I would think that it would not be a large amount. If it were true, you would see it as an increase in gas mileage.


This post about sums it up. And it eludes to something else. If you run the car on lighter weight oil it will run slightly cooler and get slightly better gas mileage. Stay with your manufacturer recommended viscosity though, I am not telling you to run lighter oil.

 

[GMBoy]

I agree that the COOLANT temp won't change. However, the OIL TEMP may cooler using Syn - but probably not much. I do notice that my Harley oil temp runs cooler with Redline V Twin or Mobil 1 V Twin oils than with conventional oil. That's a fact I can report. As for my other vehicles..they are all on a synthetic diet so I don't know there.

 

[Stelth]

My understanding is that synthetic base oils are more efficient at heat transfer. Therefore, the parts of the engine that are cooled by the oil may benefit from synthetics. As has been pointed out, the thermostat governs (assuming the cooling system is in good shape) overall engine temperature, so you wouldn't see a lower reading on your temp gauge.

 

[d00df00d]

Originally Posted By: HBCALI
Can an engine oil claim to reduce vehicle operating temperature? I thought that was a result of the cooling system. For example, will my engine run "cooler" with synthetics (let's say Mobil 1) when compared to conventional?

Seems like a vague question, but in a hot climate, anything helps. Thanks.

Coolant temperature and overall average engine temperature will be about the same. This is for the reasons others have explained.

IF (that's a big fat IF) the synthetic oil does a better job of reducing friction and/or transferring heat, hot spots due to friction may be less severe and fewer in number, and oil temperatures may be slightly lower (especially if the car has an oil cooler).

 

[440Magnum]

Originally Posted By: Stelth
My understanding is that synthetic base oils are more efficient at heat transfer.


I don't believe that either. Synthetics and conventional oils are ALL hydrocarbon liquids. They've all got the same heat capacity, thermal conductivity, etc. down to at least a couple of decimal places. Any slight difference in how effective they are at transferring heat would be related to, say, some difference in surface affinity. Polar molecules like esters might improve heat transfer slightly, but again.... its a burp in a hurricane. So small of a difference that it would be all but impossible to actually measure.

Actually, I could equally well convince myself that polar molecules would HURT heat transfer because a layer would adhere to all the metals and act as an insulator.

I just don't think it matters AT ALL.

 

[Old Mustang Guy]

Before I started reading BOB I would have sworn that synthetic oil would result in more power, less friction, cooler running, longer engine life etc. Now, I don't think so.

 

[Spawne32]

first time i ran royal purple my car ran noticeably cooler on the order of 8 degrees (datalogged). I was previously running supertech oil (because i needed something cheap). I would assume the reason you could get a cooler running engine is from less friction overall if its doing its job better then the others.

 

[Errtt]

Originally Posted By: GMBoy
I agree that the COOLANT temp won't change. However, the OIL TEMP may cooler using Syn - but probably not much. I do notice that my Harley oil temp runs cooler with Redline V Twin or Mobil 1 V Twin oils than with conventional oil. That's a fact I can report. As for my other vehicles..they are all on a synthetic diet so I don't know there.



I notice as soon as I switched my Harley to synthetic (Amsoil 20-50), it ran cooler also. I thought somethings not right with the oil temp gauge, so I replaced it and the reading was still the same, about 10 degrees or so cooler. I had a tech tell me it dissipates the heat more efficiently.
No cooling system (liquid), but the results were immediate.
I don't know - but I see it on the oil temp gauge - cooler oil temp.

 

[CATERHAM]

Yes syn' oils, particularly heavy syn' oils, tend to run cooler oil temp's than mineral oils of the same grade because they have a higher viscosity index.
The reason is, high VI oils are effectively lighter not just on start-up but at normal operating temp's for a give HTHS viscosity and lighter oils flow faster and therefore cool better than thicker oils.

 

[KrisZ]

I have a question to people noticing cooler oil temps with synthetic oil.

Was the cooler temp constant throughout the OCI, or you just checked right after the OCI and never really bothered afterwards?

But if these temps stayed lowered, and never crept up during the whole OCI, then there might be something to it.

 

[tig1]

Years ago oil temps(not coolant temp) would be a little lower with synthetic oil vs dino of the same weight. However dino has improved so not sure about today. In the early 90s Corvette started using M1 oils from the factory so that they could do away with their oil cooler. Had something to do with body design changes.

 

[d00df00d]

Originally Posted By: tig1
In the early 90s Corvette started using M1 oils from the factory so that they could do away with their oil cooler. Had something to do with body design changes.

As I understand, this was largely (or entirely) because synthetics could tolerate higher temperatures, not because they ran cooler.

 

[HTSS_TR]

I'm not sure but I think the thinner oil runs cooler than thicker oil in my E430. I don't have oil temp gauge and the Ultra Gauge doesn't have oil temp either, but according to coolant gauge and Ultra Gauge the E430 is about 4-7C (8-12F) cooler with xW20 than M1 0W40.

When I passed Death Valley on the way to Vegas in summer, the coolant temp was only 185-192F with xW20 and it was 198-205F with M1 0W40, the ambient temperature was 120F+. The speed was about 90-100+ MPH. The OEM thermostat is 185F.

On local highway at speed around 70MPH the coolant is only 180-190F with xW20 and it was 190-200F with M1 0W40.

 

[d00df00d]

Originally Posted By: HTSS_TR
I'm not sure but I think the thinner oil runs cooler than thicker oil in my E430.

It should. All else equal, thinner oil generates less drag and transfers heat better.

 

[aquariuscsm]

Imo,the only advantage to using synth oil is keeping to engine internals cleaner,thus in the long run making the engine more "efficient" per se?.

 

[CATERHAM]

Slightly off topic, but oil temp's tend to run cooler than coolant temp's in typical light duty applications but can creap higher than coolant temp's during sustained high speed driving or when a higher than normal percentage of large throttle openings are used.
And while high coolant temp's will increase oil temp's, the converse is not true particularly at speed when maximum air flow through the rad' (generally 70 mph) is achieved. The reason is that the coolant temp's is thermostatically controled while the oil is usually not.
Another observation is that oil temp's will be higher on a hot sunny day between say 11:00am and 4m when the asphalt can be very hot particularly on an exposed sump vs the same ambient temp's on a cloudy day or at night.