Coolan/Oil Temperature

[Blue636]

Alright, I'll add my own experience then. In the summer time here, my coolant temperature will get up to 220F sometimes. In the winter, I have not seen it go up any higher than 185F. I don't have an oil temp guage, but do you mean to tell me that there will be fluctuations in my coolant temperature and not my oil?

Also, how can you even begin to think that atmospheric temperatures have nothing to do with oil temps? How can you think that oil in a car driven in Antarctica is going to have the same oil temp in the same car driven in Brazil? Oil temperature will vary with the atmospheric temperature. If oil did not vary in temperature, what would be the purpose of the difference grades and viscosities? What about shearing?

Well, that's all I have to say. Apparently, you know something that all oil manufacturers don't. I'm assuming you're probably very rich.

[ March 05, 2004, 02:02 PM: Message edited by: Blue636 ]

 

[Tree Hugger]

quote:

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Originally posted by Blue636:
Alright, I'll add my own experience then. In the summer time here, my coolant temperature will get up to 220F sometimes. In the winter, I have not seen it go up any higher than 185F. I don't have an oil temp guage, but do you mean to tell me that there will be fluctuations in my coolant temperature and not my oil?

Also, how can you even begin to think that atmospheric temperatures have nothing to do with oil temps? How can you think that oil in a car driven in Antarctica is going to have the same oil temp in the same car driven in Brazil? Oil temperature will vary with the atmospheric temperature. If oil did not vary in temperature, what would be the purpose of the difference grades and viscosities? What about shearing?

Well, that's all I have to say. Apparently, you know something that all oil manufacturers don't. I'm assuming you're probably very rich.

---

Well the coolant temp in my '03 Chevy Avalanche with the 5.3L V8 stays a pretty constant 210 dF winter or summer. I don't know what your vehicle is, but I would check the thermostat if I had it, what you describe is symptomatic of either a 'failed-open' thermostat, or too low of a temperature thermostat.
My coolant (and oil) temperature fluctuate from startup to fully warm. And the starting point from which it varies is different in summer or winter. But the WORKING temperature is what I'm talking about. After it's fully warm. I have NO evidence of that varying from winter to summer (except for the one data point cited above).
If you can't understand how that can be, consider this. The oil (and coolant) are both being heated far above the ambient temperature by the engine block and then the coolant is being cooled down again by the cooling system. It's my hypothesis that the coolant is also cooling the oil down to a temperature related to its own temperature and that this is quite independent of the ambient temperature outside the engine. The only factors that could disturb this relationship would be a separate oil cooler (which few cars have) and the cooling effect of the ambient airflow on the oilpan, which I think is probably tiny.
You have multigrade oils to cope with the temperature range from startup to fully warm, that's why car manufacturers recommend different 'W' number grades, but not usually different hot number grades (e.g. 0W30, or 5W30 or 10W30)
And you have different 'hot' number grades for the requirements of different engine designs.
And shearing has NOTHING to do with this discussion.
And far from "knowing something that all oil manufacturers don't", I'm ASKING THE QUESTION, (and you're giving uninformed answers). The Car Manufacturers don't seem to be recommending a different 'hot' weight for summer and winter, and NEITHER DO THE OIL MANUFACTURERS.
I THINK we're dealing with one of those persistent myths that may have been true many years ago, but long since ceased to be true (like not rotating radial tires side to side).

 

[moribundman]

quote:

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You have multigrade oils to cope with the temperature range from startup to fully warm, that's why car manufacturers recommend different 'W' number grades, but not usually different hot number grades (e.g. 0W30, or 5W30 or 10W30)
And you have different 'hot' number grades for the requirements of different engine designs.

---

Note the different viscosities (first AND second number) my manual allows:

5w30 (not advised for high speed long distance driving)
10W-30

5W-40
10W-40

5W-50
10W-50
10W-60

15W-40
15W-50

20W-40
20W-50

Oil from 5w30 to 10W-60 is approved. That's quite a difference.

[ March 05, 2004, 03:31 PM: Message edited by: moribundman ]

 

[jsharp]

The oil temp in my Pathfinder runs right around 200 degrees year round with a stock thermostat which I think is 190 degrees. I have seen the oil temp as high as 240 in the summer but it's usually only a few degrees higher than where is runs in the winter.

So why would I want to go to a heavier oil? How much heavier would I need to go to get the same viscosity at 240 degrees in the summer as I do with a different viscosity at 200 degrees in the winter if that's the reasoning for changing weights?

I'd guess the difference long term wouldn't be enough to make any difference in engine life in the climate where I live. I think the winter/summer weight thing is a leftover from the days of straight weight oils...

 

[Tree Hugger]

Moribundman, That's quite a surprising recommendation, to me.
Mine says the values I quoted for example.
What engine> What car?

 

[moribundman]

It's a 1996 Audi A4 quattro with the 2.8 V6 12v engine. The oil chart is typical for European manufacturers. Newer Audi manuals have simplified oil charts. That's because most new cars are on extended service intervals, and OCs are due only every two years. So they have to use a true 4-season oil like 0W-30 or 0W-40.

The oil/ambient temperature chart in my manual takes into consideration low and high ambient temps, and if the used oil is a friction modified (synthetics that meet VW500.00) or a blend or mineral oil that meets VW501.01.

For example, 5w30, 5W-40, 10W30, 10W-40 mineral oils are not allowed at ambient temps above 55 degree F.

[ March 05, 2004, 04:24 PM: Message edited by: moribundman ]

 

[Tree Hugger]

I'm beginning to wonder if this might not be very (completely?) dependent on engine and car design.

And maybe everyone has a strong opinion, one way or the other, but it's more based on the cars they typically drive, and the environment where they live, rather than a general principle for all?

 

[Blue636]

quote:

---

Originally posted by Tree Hugger:
I'm beginning to wonder if this might not be very (completely?) dependent on engine and car design.

And maybe everyone has a strong opinion, one way or the other, but it's more based on the cars they typically drive, and the environment where they live, rather than a general principle for all?

---

You mentioned something earlier regaring the oil which is being consequently cooled by the effect of the coolant. That's how you related the two in your post (a few posts above). You say that the engine and the fluids will heat up to a temperature beyond the ambient temperature outside of the vehicle, and I agree. However, I believe that when the ambient temperature is very high it makes the cooling system a little less efficient. Like I said, my coolant temp shows no higher than 185 and possibly 190 in the winter. In the summer, my coolant can get as high as 225 - so, there's no way anyone can say the oil is NOT being affected by this temperature change. If the oil is being cooled, to an extent, by the cooling system then it will also run hotter when the cooling system is running much hotter.

You were asking about why anyone would use a heavier weight or "summer" weight and I mentioned shearing. You said shearing had nothing to do with the conversation but it does. Would you want to use a 20wt oil in 100 degree weather and risk it shearing down over time to a 10w or less? I wouldn't. It's not necessarily the temperature that has anything to do with it the shearing, either. But if a specific oil will shear, then it will lose the necessary viscosity range to cope with the increasing temperature. If viscosity was not important in relation to temp, I'd run a 0w-20 all year round.

 

[Jelly]

I'd like my coolant temps to stay as low as possible with my oil temps staying as close to 100C as possible.

 

[edhackett]

Tree Hugger, you are basing your comments on several very common misconceptions.

First, is that your temperature gauges are showing you what is really happening. The gauges in most modern vehicles are highly dampened. They show you what the manufactuer wants you to see over a fairly wide range of parameters. In other words, the gauge sits right at the same spot, right where it should be as long as the values it sees are within the manufacturer's "normal" range. The gauge will only move above or below it's "fixed" position once parameters move outside of that window. My Subaru's factory water temp guage will move to its "normal" position after about three miles of essentially coasting down hill on a 20F morning. It also sits at exactly that same spot pulling a long grade at 90 mph pulling 10 psi of boost on a 100F day. Do I believe that he coolant is is really exactly the same temperature under these conditions? No. The average schmoe (no offense schmoe

) gets a warm an fuzzy feeling when their temp guage stays nicely fixed at the lower third of the operating range shown on the gauge.

Second, is that ambient air flow over the oil pan has a tiny effect on the oil temperature. The effect is actually huge. The 30-40 degree sump temperature differences that I see summer to winter at a normal cruise with my WRX are almost all due to ambient air flow across the oil pan/filter. On a 100F+ day my sump temperature will drop 5 degrees by speeding up from 65 mph to 85 mph. The sump on the WRX is nothing special either. It's just a stamped steel pan tucked up behind a front splash guard. My 1959 Alfa Romeo 1300cc had a large, finned, aluminum sump with a 7L capacity. During the summer the water ran at 180F, the oil at 190F. I had to drive it at near 0F once. The water temp was 180F, the oil temp never moved off of the peg.

Third, is that manufactures don't specify heavier weight oils for higher ambient temperatures. Only in the US, and typically with US manufacurers who are up against the wall with the EPA/CAFE B.S. will you see a max of 30W recommended. The EPA requires the manufacturer to do anything short of physical threats to get you to use the oil weight that the manufactuer used for CAFE certification. I'll use my 2003 Subaru again as an example. The recommended weights are as follows:

Less than 100F: 5w30
0F to 100+F: 10W-30 10W-40

There is a note saying 5w30 is the prefered weight. (Nod to the EPA).

There is also a note saying that when using the vehicle in heavy duty applications or in desert areas to use 30, 40, 10W-50, or 20W-50.

Those recommendations are based on non-synthetic oils and are the same as what was listed for my 1995 Outback, except for 5w30 was not recommended for high speed operation.

Ed

 

[Tree Hugger]

Well, now I'm just about convinced!

Would a thermostatically controlled oil cooler materially affect this? Specifically, would it make the continued use of the (warranty required) xW30 more prudent?

Thank you,
Joe Scmoe

 

[cryptokid]

everything depends on the engine design honestly.
some engines just run hot oil temps, and some cool.
my old subaru ran such cool oil temps that i could hold my hand on the oil pan for 5 seconds at a time after 3 hours of interstate driving. i would GUESS it was running oil temps of 80C while the coolant was at 100C

running youre oil at boiling point of water is un-needed however, as water will evaporate rather quickly at temps of less than 100c, heck water evaps at 20c just as an example.
if you need to run the oil at 100C to keep water boiling off, youre having some sort of mechanical problem which needs to be fixed.

 

[TheTanSedan]

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=4;t=000196

 

[Blue636]

This is from the link "TheTanSedan" posted...

"which means that on the average, the Oil Sump temperature is always 1.2 to 1.43 times higher than the coolant temp."

Would this justify the "summer weight" oils? I mean, if my coolant is at an indicated 195-210 then I should find a multigrade with higher than a Xw-30, shouldn't I?

 

[Tree Hugger]

Also from that link, and possibly even more relevant:-
An interesting side-bar of the study was that the bulk oil temperature increased "only" 0.3 C for every 1.0 C increase in ambient (oustside) temperatures.

 

[XS650]

quote:

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Originally posted by cryptokid:

running youre oil at boiling point of water is un-needed however, as water will evaporate rather quickly at temps of less than 100c, heck water evaps at 20c just as an example.
if you need to run the oil at 100C to keep water boiling off, youre having some sort of mechanical problem which needs to be fixed.

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160F seems to not be enough but I have had engines that ran 180F oil temps stay real nice inside.

 

[TheTanSedan]

Another good read:

http://jeepsunlimited.com/forums/showthread.php?s=&threadid=477384&highlight=cooler

The best of both worlds: faster engine oil warmup & keeps oil temperature spikes under (some) control. The right set-up here would be an effective way to keep ring seal at a constant (or so I'll hypothesize). Ought to ease the load on the oil.

Plenty of good ideas.

 

[DinoOil]

My 2012 Charger has an oil temp sensor. In the summer on hot days sitting in traffic, the gauge has gone up to 225 F. In the fall and winter it can hover around 200 F and sometimes will take a long time to reach 212 F. Also, even cruising at high speeds the oil won't get excessively warm. Usually when you push the car hard the oil temp will rise quicker than usual.