Thinner oil heats up more quickly in my audi

[saaber1]

Originally Posted By: saaber1
Interesting. So Syntec 5W40 with around 6k miles is around 11.2. So it sounds like it may have more to do with the composition of the 2 oils, Syntec 5W40 vs. GC.

So now the question is, what specifically is it that makes one heat up faster then the other, base oils? other?

Great stuff! We need more of this kind of data.


I just want to verify and if so, make sure everyone understands that the Syntec 5W40 was thinner than the GC in this test.

Syntec 5W40 with 6000 miles is 11.19 cst according to UOA.

GC at about 100 miles is close to 12.2 cst.

 

[Gary Allan]

That would make it hard to attribute the difference to 1 Cst +/-

 

[zoomzoom]

Originally Posted By: np6000
Zoom, I think you would know best how repeatable this is since you were driving it.

I come from an engine test background, so I usually question my setup or test cycle when I note large differences between seemingly identical tests. Its amazing how often the throttle controllers develop a mind of their own

I usually use fuel flow, BSFC, speed, load to tell me whether or not the engine is actually running at the same conditions as the last test to make sure Im comparing apples to apples.

On another note, I was just leafing through a heat transfer text book that lists CP differently for new and used oil. One more variable to consider.


I agree that conditions are not exact..ideally you would test two oils with same mileage and under same exact conditions but
that something don't have time and resources for.

Instead this should be looked at as a data point for those two oils in my car with my kind of commute

I did noticed that my oil temp will come up slower with 5w-40(then it use to do with GC) so I did this little test and it confirmed my observations..

when it gets cold I might repeat the test with redline 5w-30 I am currently running.it should have 4-5K miles on it by December..

 

[zoomzoom]

Originally Posted By: saaber1
Originally Posted By: saaber1
Interesting. So Syntec 5W40 with around 6k miles is around 11.2. So it sounds like it may have more to do with the composition of the 2 oils, Syntec 5W40 vs. GC.

So now the question is, what specifically is it that makes one heat up faster then the other, base oils? other?

Great stuff! We need more of this kind of data.


I just want to verify and if so, make sure everyone understands that the Syntec 5W40 was thinner than the GC in this test.

Syntec 5W40 with 6000 miles is 11.19 cst according to UOA.

GC at about 100 miles is close to 12.2 cst.


It is true that Syntec 5W40 was thinner at 100C but that might not be true at lower temperatures since they have different viscosity index?

 

[friendly_jacek]

Originally Posted By: zoomzoom


It is true that Syntec 5W40 was thinner at 100C but that might not be true at lower temperatures since they have different viscosity index?


That is a possibility. syntec/GC [cst]: 80/68 at 40C and 132/155 at 25C. But, there is one more compelling reason for the difference. Used oil produces less friction compared with new oil. That effect is real and has been documented here:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1528239#Post1528239

 

[saaber1]

Originally Posted By: zoomzoom
It is true that Syntec 5W40 was thinner at 100C but that might not be true at lower temperatures since they have different viscosity index?

Right, you could use the widman calculator to come up with some approximations of the lower temp viscosities.

At about 8 min in or so we have 40C where syntec was around 63.5 according to the UOA and GC was around 68.5 (assumed, based on VOA and about 100 miles of usage and assuming no fuel dilution in that short time). So for the >8 minute portion, I think it is safe to say the GC is thicker.

 

[friendly_jacek]

Originally Posted By: saaber1

Right, you could use the widman calculator to come up with some approximations of the lower temp viscosities.

At about 8 min in or so we have 40C where syntec was around 63.5 according to the UOA and GC was around 68.5 (assumed, based on VOA and about 100 miles of usage and assuming no fuel dilution in that short time). So for the >8 minute portion, I think it is safe to say the GC is thicker.


If the syntec sheared down, the VII changed and the calculation may not work. Besides, I don't think the difference is in the viscosity.

 

[saaber1]

Originally Posted By: friendly_jacek
Besides, I don't think the difference is in the viscosity.


Right that is what I am saying, that viscosity alone may not be the reason. The 0W30 at 100 miles is thicker than the 5W40 at 6000 miles. So what at first appeared that the thinner oil heated up faster than the thicker oil is actually the opposite, and also the viscosities are real close.

So again my question is if viscosity is not the reason, then what is? Base oil differences? The fact that one oil is new vs. the other has 6000 miles? Other?

 

[zoomzoom]

Originally Posted By: friendly_jacek
Originally Posted By: zoomzoom


It is true that Syntec 5W40 was thinner at 100C but that might not be true at lower temperatures since they have different viscosity index?


That is a possibility. syntec/GC [cst]: 80/68 at 40C and 132/155 at 25C. But, there is one more compelling reason for the difference. Used oil produces less friction compared with new oil. That effect is real and has been documented here:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1528239#Post1528239


funny you say this..I recall having slightly lower oil temperatures at second track event with GC in the engine despite the higher ambient temperatures..hmmm