synthetic motor oil : does lower temp. gage >

[smokey1]

well , when I did use regular oil to about 74,000 miles on our 2000 PRIZM ( Corolla ) the temp gauge read at exactly 1/2 , then when switched to 5w30 M1 synthetic the gauge lowered by about 2-3/16 ths of an inch . Then following oil change went w/ PENNZOIL PLATINUM 5w30 and the temp gauge remained the same . So , was told could be thermostat , went to TOYO service center and had anti-freeze changed ( figure time for new anyways ) and replaced old thermostat w/ TOYOTA thermostat . Guess what , the temperature gauge remains the same . Therefore , has to be the synthetic helping to keep block cooler . Last , was over 90 degrees and humid , so had to use the A.C. and the gauge never budged , before w/ the dino on day like today the gauge would sometimes rise about 1-2 sixteenths of an inch . This included plenty of city driving and 70-72 m.p.h. on the highway ( w/ AC on at times when climbing long steep hills , putting her to the test , w/ plenty of power to boot )

. Only downside is the valve cover gasket could be seeping since the switch ( cleaned around it , keep an eye on it )

. Let the debate begin .

 

[globey]

I recently switched to a 5w30 full synthetic and commented to my friend about the same thing. I also noticed a slight decrease in the temperature guage after the switch. I'm not hallucinating or looking for things...the guage would sit squarely (consistently...my vehicle only has 8K on the odometer)in the middle before the change.

 

[kgb007stb]

I can confirm this, but with a 2-cycle engine. In an air cooled engine it is much easier to control for some variables such ambient temp and since they are small and mobile, load can also be fairly easily re-created from one test to another.
Mine engine had a difference of roughly 30-40C at operating temperature when tested on a mineral VS. synthetic 2-cycle oil. I think the actual numbers came to 160C vs 200C, huge difference. We are not talking about idle, I ran it at 80% WOT using a RPM meter with the same exact load, and same exact ambient temperature. I used same exact gas, with same exact oil to gas mix ratio.

 

[65cuda]

Actually I don't see where the change in oil would decrease or increase the temperature guage. Afterall the temp is controlled by the thermostat and it is meant to keep the engine operating at a certain temp. Now synthetic I would think would reduce the work that the cooling would have to do but other than that unless the cooling system was borderline I don't see what effect it would make. I know on my cars that I switched to syn I can't say that I noticed any difference in the gauge.

 

[Thatwouldbegreat]

Where I notice a difference is on the oil temp gauge when I use Redline and more recently Eneos.

 

[jorton]

If synthetic reduces friction I would call it an engine oil upgrade. Good for folks who expect to keep a car for a long time, like 5 - 7 years. Does it also improve fuel economy by .5 - 1 mpg?

(Does it really reduce friction?)

 

[Gary Allan]

does lower temp. gage


I say ...maybe. Conditions and restrictions apply. For the average engine? No. I have to say that with my Mitsubishi engine, with 0w-10 and just bypassing whatever can pass through a 3/8" hose, that I have a hard time maintaining oil temp above 175F AND keeping the coolant anywhere near 190-195F. There's more to supporting my notion here ..but I'm too lazy at the moment to catalog it all out now.

Effectively it means that the thinner the oil, comparatively speaking, the easier it is to reject its heat through the various surfaces (pan, etc.). The oil temp is a function of, mostly, the thermal back pressure that's not exiting the engine via the exhaust or the cooling jacket. Now in the vast majority of engines it's really hard to trump the btu's absorbed by the heads and cylinder walls, but I can see no other reason when my oil temps used to peak @ 215F+/- unexchanged ..and now do not when coolant exchanged (again, there's more to it). A 3/8" line for coolant ..and auxiliary oil cooling, shouldn't trump the thermal output of the engine into the cooling jacket ....but it does

 

[Ramblin Fever]

5-7yrs?? Come on peep's - try doing 10, 15, or even 22yrs with the same vehicle.

It REALLY does help you get ahead financially, as long as it's not having to be repaired every other month.

Yes, I too, have noticed a very slight change in temp; however, I didn't notice this before when my 8-9yr old radiator was still in use. Those whose gauges don't fluctuate at all, for any reason, my have some mild blockage.

 

[Titan]

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Those whose gauges don't fluctuate at all, for any reason, my have some mild blockage.

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Disagree. Those whose coolant temperatures don't budge have a perfectly functioning system. If the system is somewhat compromised, THEN you could start seeing variations...such as the temp will rise when under more stressful thermal conditions.

Taken a step further, if changing oil results in a change in your coolant temperature, you have a marginally adequately functioning cooling system, OR (and this is not likely with a modern passenger vehicle), you have a cooling system that has excess efficiency capacity for that vehicle (which would include a malfunctioning thermostat/temp regulatory mechanism, it could also include excessive oil cooler capacity).

The point is, there is a narrow range of temperatures that are close to Ideal with respect to combustion and thermal stress on the various pieces of the system. A properly functioning system should have a coolant temperature that is consistant, no matter what oil you have in the sump, assuming the oil is of the correct viscosity range.

 

[Curious Kid]

For those whose coolant temp gauge doesn't move at all might not just have a perfectly function system, as in the case of a '90 volvo, the gauge had a compensating circuit of sorts that would have the needle remain constant within a predetermined signal range from the sensor - going higher or lower than this window would than have the gauge read beyond the norm. I found this out after the circuit went bad giving cold or hot readings out of the blue. It's since bypassed and provides a more realtime reading which varies around or just below it's previously horizontal position.

Take care.

 

[Curious Kid]

Oh, as far as oil temps - I wouldn't per say use my coolant gauge to tell me much...It sometimes happens that my radiator fan cycles before my oil is above 180 degrees f. Run some more tests by switching back to a conventional with similar viscosity characteristics within the operable temp range. The likelihood of the oil having less VII's for a synthetic formula over a conventional as often argued around here might have something going for it, in that the overall viscosity of the fluid is then more consistent - higher rate of thermal transfer???

There also are the ingredients in the lubricant formula that neither you or I are going to know about as they don't show themselves in the average oil analysis, and of which play a role in this as well I would think, however indirectly.?.

Interesting.

 

[flatlandtacoma]

Your coolant temperature is controlled by the thermostat ONLY.

Now, unless your engine
(1) is now running so cold that the thermostat doesn't open AT ALL, or

(2) WAS running so hot that the thermostat was wide open constantly,

then there is absolutely no way that changing the oil can affect your coolant temperature. Anyone who says otherwise has been smoking too many buttery smooth baked potatoes.

 

[aquariuscsm]

Maybe syns work in the same aspect as Water Wetter. Just by providing more lubrication/cooling efficiency in the cylinder heads,not necessarily in the radiator itself.

I`ve also wondered if the stock temp gauges are impeccably accurate,like most say stock oil pressure gauges are not,thus having to measure oil pressure with an aftermarket gauge.

I know with syn/Water Wetter,my engine bay seems cooler after a long run,but it could just be a layman`s imagination.

 

[Challenger71]

you're right on all points and it's not you hallucinating, synthectic does reduce crankcase temps. Also, if you use waterwetter in conjunction with synthetic it will augment the cooling effect.

Quote:

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Maybe syns work in the same aspect as Water Wetter. Just by providing more lubrication/cooling efficiency in the cylinder heads,not necessarily in the radiator itself.

I`ve also wondered if the stock temp gauges are impeccably accurate,like most say stock oil pressure gauges are not,thus having to measure oil pressure with an aftermarket gauge.

I know with syn/Water Wetter,my engine bay seems cooler after a long run,but it could just be a layman`s imagination.

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[Gary Allan]

Quote:

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Your coolant temperature is controlled by the thermostat ONLY.

Now, unless your engine
(1) is now running so cold that the thermostat doesn't open AT ALL, or

(2) WAS running so hot that the thermostat was wide open constantly,

then there is absolutely no way that changing the oil can affect your coolant temperature. Anyone who says otherwise has been smoking too many buttery smooth baked potatoes.

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You're correct on all points ...typically. I'll venture to say that you've never seen an engine where the ability to maintain 190 coolant temp is a challenge. I've had a tremendous education with my Mitsubishi 3.0. A stark contrast to anything with a full flow bypass circuit that's pretty common. Just a 3/8" bypass line drives my coolant temp BELOW thermostat threshold (195F spec).

I wish I could communicate my frustration with not having enough abundant thermal excess to get the results that I want. Most of us have full flow (5/8") bypass circuits that allow our quick warmups and, effectively, make the radiator and "also ran". This isn't the case in all engines. Some are far more delicately balanced and respond differently to alterations (which may include going to a synth).

Granted, 99% of the time it would never be detected.

 

[Titan]

Quote:

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....The likelihood of the oil having less VII's for a synthetic formula over a conventional as often argued around here might have something going for it, in that the overall viscosity of the fluid is then more consistent - higher rate of thermal transfer???

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I can't imagine how consistant viscosity can have anything to do with a higher rate of thermal transfer....

 

[Thatwouldbegreat]

I've read that synthetics can have up to 10% better heat transfer, and that 1/3 of engine cooling can be from the engine oil.

I wonder if synthetic is better at heat transfer , or that many synthetics have fewer additives and that is why heat transfer is better....or both.

 

[globey]

Ok, so what's the deal? Have I been smoking too many "buttery smooth baked potatoes" as flatlandtacoma has stated or is it possible to see a dip with a switch to syn? I am reading points on both sides, but I know what my it reads and I doubt very much I have a malfunction on my fairly new vehicle. The temp has maintained a steady temp.

 

[Gary Allan]

No one said that this was even "likely" to ever be detected. Typically there are so many excess btu's for the coolant to reject that having the oil soak up a few more doesn't even account for a blip on the radar. We're merely discussing and exploring the cause and effect relationship.

Keep in mind you never saw a UOA at one time too. You never knew whether you were doing a good job or a poor one ..had no idea what TBN was ..oxidation ..etc...etc. It looked the same from your point of view (apply lateral principle as needed).

 

[Titan]

Quote:

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Ok, so what's the deal? Have I been smoking too many "buttery smooth baked potatoes" as flatlandtacoma has stated or is it possible to see a dip with a switch to syn? I am reading points on both sides, but I know what my it reads and I doubt very much I have a malfunction on my fairly new vehicle. The temp has maintained a steady temp.

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Here's the deal: in a passenger vehicle with appropriately sized, fully functional cooling system, changing from "dino" to "synthetic" oils of the same viscosity, or even anywhere near the same viscosity, will NOT result in any change of the coolant gauge temperature, when the comparisons are done under similar and "usual" conditions.