Thinner oil heats up more quickly in my audi

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I did this test while ago. I collected the oil temperature data from my car on my way to work. Just before I changed from GC 0w-30 to Syntec 5w-40 or the other way around. as you can see from the chart GC comes up to temperature quicker even though it starts few degrees cooler.
 
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Cool data. I'm assuming that the oil temp. stabilized after 20min at 100C?
 
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I think you need some more data to add to the plot before you draw conclusions; engine speed & wheel speed, engine torque, fuel flow, bsfc, and a bunch of others. Not to mention oil at the end of its drain interval will have different properties than at the start of a drain interval.
 
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That would support the theory that a thinner oil heats up faster? Not sure about it starting cooler, it can only be as cold as ambient temps? That is assuming it sat over night and completely cooled off.
 

zoomzoom

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 Originally Posted By: hate2work
Interesting, but why does the GC start at a colder temp?
Because that morning was colder than the one I collected data with 5w-40. Car is parked outside so starting oil temperature will be whatever ambient was that morning.
 
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Cool data! How many miles were on each oil at the time of testing? We know virgin syntec 5W40 is 13.7 cst and GC is 12.2 or so. So when the oil is new there is a roughly 1.5 difference in kv100 but if the 5w40 was run for a long time for example the visc. difference would be less.
 
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 Originally Posted By: zoomzoom
 Originally Posted By: hate2work
Interesting, but why does the GC start at a colder temp?
Because that morning was colder than the one I collected data with 5w-40. Car is parked outside so starting oil temperature will be whatever ambient was that morning.
That is what I thought, and because they started at different temps and not the exact same temp the thinner grade oil would have heated up even faster, in this graph.
 

zoomzoom

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 Originally Posted By: saaber1
Cool data! How many miles were on each oil at the time of testing? We know virgin syntec 5W40 is 13.7 cst and GC is 12.2 or so. So when the oil is new there is a roughly 1.5 difference in kv100 but if the 5w40 was run for a long time for example the visc. difference would be less.
after checking back my previous UOA's I tested Syntec 5w-40 with about 6K miles on it(UOA with 12/18/05 date on it) then switched to GC and collected data with probably less then hundred miles on the oil...
 
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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.
 
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Zoom, I think your car come with a coolant to oil heat exchanger. Am I right? The GC has sheared more than one typically sees. How many track sessions did you have with the last oil? The previous OCI's were GC as well? Any track sessions previously?
 
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ok, time to try this a different way: If I put one 1 KW of energy to heat oil A and 1.5 KW of energy to heat oil B, what do you you learn if I tell you oil B heats up faster? Not to discredit what your trying to do here, but you need more information to aid you in your analysis.
 
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If it had an exchanger it should have warmed much sooner over the time span. He would have been soaking up btu's that would normally be heading out the radiator very early in the event and would have soaked up btu's continuously before that threshold was reached. Most that I've polled (noticed) in ..like VW/AUDI.. reach coolant like temps at about 9miles/minutes versus the typical 12-15miles/20 minutes. That matches my own observations.
 
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 Originally Posted By: np6000
ok, time to try this a different way: If I put one 1 KW of energy to heat oil A and 1.5 KW of energy to heat oil B, what do you you learn if I tell you oil B heats up faster? Not to discredit what your trying to do here, but you need more information to aid you in your analysis.
Is the volume of oil A equal to the volume of oil B?
 

zoomzoom

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 Originally Posted By: CATERHAM
Zoom, I think your car come with a coolant to oil heat exchanger. Am I right? The GC has sheared more than one typically sees. How many track sessions did you have with the last oil? The previous OCI's were GC as well? Any track sessions previously?
You are right car has coolant/oil heat exchanger like most vw/audi cars. last UOA was 2 track events with 2 days each so 4 total track days. UOA prior to that has 2 track days while other UOAs don't have any track days, just some spirited driving from time to time. so oils analyzed going backwards are GC GC GC GC BC(5w-40) and delavac 15w-40(with auto-rx)
 

zoomzoom

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 Originally Posted By: np6000
ok, time to try this a different way: If I put one 1 KW of energy to heat oil A and 1.5 KW of energy to heat oil B, what do you you learn if I tell you oil B heats up faster? Not to discredit what your trying to do here, but you need more information to aid you in your analysis.
this data was taken on my regular commute to work so I would say that energy input into both oils was very similar.
 

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IMO, you need to plot load, or at least correlate average load to the warmup slope. This would help a lot. I will say that folks in the BMW 1-series forum have claimed the same thing often.
 
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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 :P 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.
 

JAG

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Look at the viscosity in the UOA. The actual oil viscosities that the engine experienced during these tests may not have been consistent with GC being the less viscous of the two. Formulations and oil age are different too. To be safe I would not draw any general conclusions from these two tests. It is interesting data though.
 
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