Oil temps w/r to ambient temps - plotted for my VW Golf Sportwagen

[TiGeo]

Anytime you have more air flow through a cooler, it's going to decrease the outlet temperature of the fluid being cooled. This is also true with coolant radiators that feed coolant-to-oil coolers since those coolers feed off the cold side of the radiator. At highway speeds vs city speeds, the engine's coolant temperature coming out the cold side of the radiator will be cooler too.


It won't be low enough to make much difference ... I'd like to see formal data of how much cooler, especially on a vehicle with an oil cooler. A thicker oil if a few degrees hotter will still provide better viscosity/MOFT protection between moving parts.

PS - wish you could use the quote function. Just hit the View attachment 109031button.

My car's oil is always hotter on the highway then in town - when I come off the highway to drive home after a longer highway drive/commute, my oil temp will drop 10 degrees. Oil temp is directly proportional to RPM on my car.

 

[Thermo1223]

I look at my oil temps all the time in my VW Sportwagen and finally plotted them up to see what is showed. These data were collected on the same route (and after enough time that they stabilized) - a 45 mile highway drive so speed and driving style are consistent with ambient being the primary variable. It should also be noted that oil type would also be a variable but all were 5W40s with the VW502 00 approval; I have seen no variation w/r to oil brand or when I change my oil etc. Extrapolation with red dashed lines on either side. This pretty much nails it in terms of low 200s in winter and low-to-mid 220s in summer on my drive. The graph would shift down for around-town driving where speeds/RPM are lower and shift up for aggressive driving - I have seen 235 on the track with sustained triple-digit driving. I see posts from time to time here about oil temps and over in the VW world/FB pages/forums I see comments about XYZ oil dropped my temps 10 degrees etc. but I call BS on those posts - oil temp variation being reported is most likely due to simply not controlling the variables for the data point collection or understanding that the oil temps will fluctuate with RPM/speed.

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To further expand on this. 2.0T Tiguan engine oil temps are even cooler in normal day-day driving. The dash reading hardly goes above 200F unless really pushing a hill for an extended time and then it never goes past 210F. I got it to read 215F once by doing a lot of high speed passing on a 70MPH speed limit highway. Heck even yesterday in our sweltering temps of 100F+ it stuck around 198F.

 

[Jetronic]

My car's oil is always hotter on the highway then in town - when I come off the highway to drive home after a longer highway drive/commute, my oil temp will drop 10 degrees. Oil temp is directly proportional to RPM on my car.

I've found this to always be the case., the influence of ambient temps and loads is minimal

 

[TiGeo]

I've found this to always be the case., the influence of ambient temps and loads is minimal

I don't agree (for my car). Ambient temp influences it ~4 deg oil temp for every 10 deg ambient per my graph. Load has a big influece....at highway speeds any increase in slope will net an increase in oil temps.

 

[Jetronic]

the difference between across rpm range is bigger than for ambient temps. Especially on the cars with decent size oil coolers. The ones I had came with a thermostat too.

RPM made 35 ish degrees difference from low to high, but dropped in a minute or so after lifting.

 

[FZ1]

I look at my oil temps all the time in my VW Sportwagen and finally plotted them up to see what is showed. These data were collected on the same route (and after enough time that they stabilized) - a 45 mile highway drive so speed and driving style are consistent with ambient being the primary variable. It should also be noted that oil type would also be a variable but all were 5W40s with the VW502 00 approval; I have seen no variation w/r to oil brand or when I change my oil etc. Extrapolation with red dashed lines on either side. This pretty much nails it in terms of low 200s in winter and low-to-mid 220s in summer on my drive. The graph would shift down for around-town driving where speeds/RPM are lower and shift up for aggressive driving - I have seen 235 on the track with sustained triple-digit driving. I see posts from time to time here about oil temps and over in the VW world/FB pages/forums I see comments about XYZ oil dropped my temps 10 degrees etc. but I call BS on those posts - oil temp variation being reported is most likely due to simply not controlling the variables for the data point collection or understanding that the oil temps will fluctuate with RPM/speed.

View attachment 53289

Good info for those of us, without, temp gauges. So, if you over laid the time from startup to oil temps, what would that look like? Ball park is ok.

 

[TiGeo]

Good info for those of us, without, temp gauges. So, if you over laid the time from startup to oil temps, what would that look like? Ball park is ok.

Each data point is about 30 min into the same highway drive so at full temp/stabilized.

 

[FZ1]

Each data point is about 30 min into the same highway drive so at full temp/stabilized.

Thanks, man.

 

[TiGeo]

MOAR data! Here is an update adding the HPL Euro oil I am current running. Bottom line, no difference here. Any slight variation in the trend line slopes is related to simply not having a full range of ambient temperatures when I ran each oil which is seasonal. Info on the control variables here are listed above somewhere. It just de-bunks a common online comment I read that I tried XYZ oil (same viscosity!) and it lowered my temps 10 degrees - not happening in normal conditions.

View attachment 108740

I'll say that since these data were collected and I've been running HPL for a few years, I *think* I am seeing higher temps out in the 90-100 deg ambients...more like 223-225 on this drive which is somewhat indicated by this graph with the yellow data points being slightly higher across the board. Probably due to the v. high HTHS value.

 

[SHOZ]

I would think most newer cars with the variable valve timing would have an OE sender that you can access though OBDII. My 2008 doesn't but the 2010 does.

I check my oil pressure at 50 mph and 2k rpm after the oil temp hits it's peak temp, and it's 48 psi using 5w40. 5w30 might be a pound or two lower. When new it was 50 psi and 50 mph and 2k rpm on 0w40. 140k miles on it now.

 

[oil pan 4]

I've observed this in my 2002 Tahoe last year. A 20*F day in January and 100*F in July, the operating oil temp on the same drive was
EDIT: Oil capacity on that engine is 6 quarts, and it cruises on the highway at 1500-1800 rpm.

I think when you edited the temperature number you posted got deleted.

 

[RDY4WAR]

I think when you edited the temperature number you posted got deleted.

It seems it did. oops. The difference in operating oil temp was just +8°F. I don't think it cares too much about ambient temp when it's surrounded by 200°F coolant, passing through 275°F bearings, and splashing on 450°F cylinder walls. Now maybe if this was an older, all iron V8 with only 5 quarts capacity, it might make a bigger difference.

 

[Yolo]

I would think a thinner oil transfers heat better than a thicker oil, no? So all things being equal and I’m not hitting ridiculously high oil temps, wouldn’t I benefit to run a 0w20 in an engine that calls for it instead of running 10W30 and pushing temperatures higher?

 

[oil pan 4]

It seems it did. oops. The difference in operating oil temp was just +8°F. I don't think it cares too much about ambient temp when it's surrounded by 200°F coolant, passing through 275°F bearings, and splashing on 450°F cylinder walls. Now maybe if this was an older, all iron V8 with only 5 quarts capacity, it might make a bigger difference.

My 5qt oil system dodge seems to be stay fairly close to the coolant temp too. Well that's a good thing.

 

[oil pan 4]

I would think a thinner oil transfers heat better than a thicker oil, no? So all things being equal and I’m not hitting ridiculously high oil temps, wouldn’t I benefit to run a 0w20 in an engine that calls for it instead of running 10W30 and pushing temperatures higher?

Maybe but not really. The most important trait of an oil is it's viscosity. By the 1960s mechanic engineers figured that the ideal viscosity of oil is about 10 to 12 cSt. So I'm not going to argue with that finding. An oil that ends with 20 hits 10cSt at like 180f and is usually around 7cSt if you're lucky at 220f.

 

[ZeeOSix]

^^^ Yep, having more HTHS viscosity resulting in more MOFT for added wear protection is still going to happen, and be overall better, even if the oil temp goes up a few degrees. Many sports car makers recommend higher viscosity for track use for a reason. And some like Toyota recommend higher viscosity for high speed or harder use conditions.