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

TiGeo

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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.

Capture.JPG
 
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My 1.4T DGXA is about 20 degrees cooler... 180F winter and will hit 200F during my summer commutes. And, it gets warm in Florida during the summer. I switched from 0w20 to 0w40 and didn't notice any running oil temperature difference. My next step is an aftermarket oil temp sender/gauge to see how accurate the OE gauge is. My OE gauge kicks in at 122F and is just --- until then. During engine break-in, it hit 220F during normal driving, gradually dropped as the odometer miles increased, and about 700 miles for oil temp to peak at 200F and never less during the summer. That is when I did my 1st OCI.
 

OVERKILL

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Great post!

A couple questions:
1. Does this engine have a coolant/oil heat exchanger?
2. How closely does coolant temp follow?

I track the oil temps in our vehicles as well, but since they both have coolant/oil heat exchangers, the temp tends to stay very close to the same year round. Of course in the winter it takes longer for those temps to come up.
 
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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 <10*F difference. No oil cooler. The greatest difference I noticed was on warmup on the cold days. The oil got up to temperature much faster when I would drive off slowly vs letting it idle. In either case though, the oil would reach about 180-190*F, stall for a couple of minutes, and then continue easing on up to 210-220*F. My theory of that is condensation evaporating off.

EDIT: Oil capacity on that engine is 6 quarts, and it cruises on the highway at 1500-1800 rpm.
 
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Good data. And then of course higher RPM on the the track contributed to yet higher temps which of course leads to a lower viscosity at operating temp. I think we might see some contributors who don’t get the same results due to different engine configurations and the use of a factory type oil cooler.

What RPM and engine speed did you cruise at?

Thanks for the post.
 

TiGeo

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A few responses to questions above.

No oil cooler.
Cruising RPM for this drive is ~2-2.5K so ~60-70mph.
Coolant temp is a dummy gauge/readout - says 194. I can log the actual temps but haven't.

Also, while I show 3 data points, I have "collected" these data over 60K miles of driving but looking at my oil temps vs. ambient A LOT! The graph nails it.
 
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Decades ago driving truck from San Francisco to the LA basin and San Diego climbing the grape vine hill loaded when the temps were over 100 gave amuch higher temps on all the gauges than when cold in the winter. The AC seemed to blow colder in the winter as well.
 
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I take that back - yes, there is an oil cooler. It's on the side of the filter unit on top. I was thinking the more traditional front-mounted radiator style.
View attachment 53319
I know what you mean. It's not a proper oil cooler but it's better than nothing. I would have been surprised if VW had put away with their traditional oil cooler.
 

OVERKILL

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I take that back - yes, there is an oil cooler. It's on the side of the filter unit on top. I was thinking the more traditional front-mounted radiator style.
View attachment 53319

Looks small, but should keep oil temps reasonably under control.

These coolant/oil heat exchanges have become pretty standard as they work to rapidly heat the oil and also keep it from getting too hot. This helps fuel economy and durability.

This is the one for my 6.4L:
1617910546228.jpg
 

ZeeOSix

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I take that back - yes, there is an oil cooler. It's on the side of the filter unit on top. I was thinking the more traditional front-mounted radiator style.
View attachment 53319
I can't tell if that cooler has coolant flowing through it (like OVERKILL's above), or it's just an oil to ambient air type cooler.
 

OVERKILL

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I can't tell if that cooler has coolant flowing through it (like OVERKILL's above), or it's just an oil to ambient air type cooler.
Here are some other views:
1617911700672.jpg


Installed:
1617911730059.jpg


So it looks like the coolant flows through the single inlet or outlet on the unit and in or out of the block in the lower hole in the mount and the oil passes through it either before or after the filter. It's clearly quite small.
 
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