Oil Weight and Ambient Temperatures

[ccap41]

Originally Posted By: OVERKILL
Originally Posted By: ccap41
Originally Posted By: philipp10
Originally Posted By: dlundblad
I asked this before, but didnt get a straight answer.

Whats the point of running a thicker running weight in extreme heat? We see here that (some) Australians and folks in the Middle East like a 50 or 60 weight oil. Wouldn't the radiator keep oil temperature somewhat in check and prevent any oil related failures? I would also think an oil cooler would be a standard option for vehicles in these regions. We also see engines that spec a much thicker weight in Europe and the other mentioned regions while the identical US version will take a 20 or 30 weight oil. (It has been mentioned here that a European car's severe use yields a thicker oil.. high autobahn speeds for example?)

I don't understand the reason behind any of this. In the US, thin seems to be in while other places are still using a thicker oil.

I think his question is, since all cars have a cooling system, then other than during warm up, why spec different oils? In effect, a car in Minnesota in winter and a car in Florida in summer, after warm-up should both see the same oil temperature, so why spec a diffent oil.

My answer is, warm-up is a killer of engines. That's when most wear occurs. however, if you are in a warm climate, might as well spec a heavier oil to take advantage of the fact you can.


From my readings you are spot on. The warm up process is what harms the engine more than anything else(lubrication-wise). Starting thinner helps things flow at much cooler temperatures and there are a lot of drivers who only make 10 minute trips meaning things are even up to temp when you're already parking. That is one reason I run a thinner oil than spec. I make a lot of 5 mile and under trips and with a thinner oil it is at least flowing the way my vehicle needs when I shut it down, even if it isn't all the way warmed up yet.


It isn't the flow of the lubricant that effects wear during warm-up. The oil is pumping and flowing just fine if it is 0w-20 or 5w-50 assuming it isn't -40C out. The issue has several components to it:

- Fit of components when cold is different than when warm. Pistons are looser in their bores. This is one reason some engines have piston slap.
- Fit of rings on cylinder walls is poorer partially due to the first point, which results in blow by gasses going pasting the rings into the crankcase
- Fuel wash on the cylinder walls from the enrichment cycle and cooler cylinder temps. This washes the lubrication from the walls as well.
- Additive heat activation temperature. This is a huge contributor. The additive package in the lubricant, certain components require heat to activate. Member bobbydevro posted on this (as did Shannow) quite recently actually.

This is why we have start-up wear. Once the engine is up to temp; once the additives are activated, parts fit properly, blow-by is reduced, fuel and moisture are flashed off....etc. Then wear becomes as close to zero as it can get.

Thank you, very good information.

 

[CATERHAM]

Originally Posted By: dlundblad
So moral of the story, if one sees 115*F+ days on a normal basis, going up a weight or 2 isn't such a bad idea.

Actually it is bad idea. Heavier oils grades require higher oil temp's to avoid reduced oil flow.
Driving normally under high ambient temp's will not raise oil temp's above the normal range. It takes lots of WOT and constant high rev's to do that if it's going to happen at all.

With a modern engine the best advice is to run the lightest oil grade recommended by the manufacturer. If a 20 grade is recommended that's all the engine requires to satisfy it's viscosity demands under the most extreme usage.
When heavier alternate grades are specified, that's what the engine will tolerate particularly in warmer climes where lighter grades may not be as readily available and/or are more costly.

 

[aquariuscsm]

Overkill's explanation of cold vs hot engine components is spot on imo. That's why always allow my engine to warm up instead of starting it and immediately hammering the throttle. I had a neighbor who use to do that with her V6 Mustang and it'd smoke like crazy and sound like the engine was going to fall to pieces.

As to ambient temp and oil temps,ambient temps do affect oil temps. My 86 300ZX turbo had an oem oil temp gauge and the ambient temp always had an effect on oil temp.

 

[Ken2]

The coolant temperature is measured only at the sensor location, usually in the head. On a hot day the "cold" tank of the radiator will be quite warm due to a high rate of flow through the radiator, and the lower part of the water jacket around the cylinders will be quite warm. On a cold day the radiator cold tank will be very cold due to a low rate of flow and the cold air through the radiator, and the lower water jackets will be very cool.

Where does the heat in oil go? Part is conducted through the metal to the cooling water. The cooler these parts are, the cooler the oil will be. Part is conducted through the metal of the oil pan and the valve cover to the passing air. The hotter the air under the hood, the hotter the oil will remain. If an oil cooler is fitted (not on many cars), it is either cooled by air or by coolant. My turbo Volvo had its oil cooler in the radiator hot tank with a thermostatic valve that sent oil through it when the oil was hot. (Keep in mind that 190°F for coolant is good. 220°F for oil is good.) An air-cooled oil cooler is even more closely related to air temperature.

So...engine oil in most vehicles will be highly related to air temperature. Many vehicles have an oil recommendation chart that shows the allowable oil viscosities for different ambient temperature ranges. In real heat like the U.S. southwest, there is nothing wrong with going up one viscosity grade in the heat of summer. In frigid winters, consider going down one "W" grade. My car calls for 5W-20 all the time, but also allows 5W-30, and I'd use 10W-30 in the summer if I lived in Arizona. My water cooled motorcycle calls for 10W-40 all the time, but I'd use 20W-50 or 15W-50 in very hot climates and diesel 10W-30 or 5W-30 if I rode in very cold winters. Other things being equal (which they never are), oil film strength relates directly with the actual oil viscosity at the temperature inside the bearing. And, bearing and engine design matters greatly. A gas turbine is made to run with 5 weight oil. A steam turbine (up to 1400°F steam temperature) is made to run with 30 wt, as are the crankcase bearings of of a huge diesel developing 7,500 hp per cylinder.

As to different recommendations for different countries, while climate matters, custom also matters. The engines are often very tolerant of different oil viscosities. Recommending the oil that the customer feels good about helps sales. Much like the American way of cheap oil every 3000 miles or the European way of very good (expensive) oil every 10,000 or 15,000 miles.

 

[Clevy]

Ambient temps affect m charger about 20f.
For example during summer on the highway at 70mph oil temps stabilize at 213f with 5w-20. In the winter it's around 190f.
Using 0w-40 lowers oil temps a bit too according to my digital oil temp display.

 

[Clevy]

Anyways if there aren't any oil temp controls suck as a cooler or heat exchanger ambient temps will affect oil temps so in the heat of summer oil temps MAY elevate enough to affect film strength thus going a grade thicker will improve oil film thickness at higher temps.

 

[CATERHAM]

Originally Posted By: Clevy
Anyways if there aren't any oil temp controls suck as a cooler or heat exchanger ambient temps will affect oil temps so in the heat of summer oil temps MAY elevate enough to affect film strength thus going a grade thicker will improve oil film thickness at higher temps.


Hot summer temp's especially hot asphalt temp's that radiate heat to the oil sump at mid-day can raise oil temp's but never enough to be concerned about. It's extreme usage under high ambient temp' conditions involving high rev's that will maximize oil temp's.
But remember the engineers have of course factored this all in to the lightest grade they recommend.

 

[HTSS_TR]

Originally Posted By: OVERKILL
Oil temp may or may not correlate well with coolant temp.

Shannow was able to significantly drive up his oil temp just driving in a lower gear for example.

It isn't until he is north of 150Mph that the oil temp starts to come up, and then continues to go up from 90C resting to 110-115C under high load. (From 194F to 240F).

European cars, especially high performance cars such as M5, require thicker oil because of sustain high speed high RPM driving on Autobahn.

According to the video, M5's oil temp was around 90C at speed below 100 MPH, climbed to 110-115C at speed above 170-180 MPH, for North America driving sustained speed(hours on end) is around 80-90 MPH or less, otherwise you can easily get ticket.

The point is, viscosity of xW30(even xW20) in a car driving at 80 MPH with 90C oil temp is as thick or thicker than xW40 in the same car driving at 180 MPH with 115C oil temp.

Oil grade for North American driving may be too thin for the same car in another country, same for oil grade for German cars is too thick for the same car driven in North America.

The exception is, if I track my cars then I should use appropriate oil, which may be 1 or 2 grades thicker than recommended by manufacture.

 

[Nate1979]

Originally Posted By: CATERHAM
Originally Posted By: Clevy
Anyways if there aren't any oil temp controls suck as a cooler or heat exchanger ambient temps will affect oil temps so in the heat of summer oil temps MAY elevate enough to affect film strength thus going a grade thicker will improve oil film thickness at higher temps.


Hot summer temp's especially hot asphalt temp's that radiate heat to the oil sump at mid-day can raise oil temp's but never enough to be concerned about. It's extreme usage under high ambient temp' conditions involving high rev's that will maximize oil temp's.
But remember the engineers have of course factored this all in to the lightest grade they recommend.


Or the manufacturer recommends to run a thicker oil when under those extreme conditions. I guess you actually have to read the Owners manual.

 

[CATERHAM]

Originally Posted By: Nate1979
Originally Posted By: CATERHAM
Originally Posted By: Clevy
Anyways if there aren't any oil temp controls suck as a cooler or heat exchanger ambient temps will affect oil temps so in the heat of summer oil temps MAY elevate enough to affect film strength thus going a grade thicker will improve oil film thickness at higher temps.


Hot summer temp's especially hot asphalt temp's that radiate heat to the oil sump at mid-day can raise oil temp's but never enough to be concerned about. It's extreme usage under high ambient temp' conditions involving high rev's that will maximize oil temp's.
But remember the engineers have of course factored this all in to the lightest grade they recommend.


Or the manufacturer recommends to run a thicker oil when under those extreme conditions. I guess you actually have to read the Owners manual.

Yes you have to read the manual carefully and interpret what's said correctly.
Toyota for example uses the phrase a "heavier grade may be more suitable." That can mean any number of things including less oil consumption.
But if a heavier grade isn't actually required to satisfy the warranty one can correctly assume the lubrication requirements on the lightest specified oil grade are more than being met.

 

[bblackmon19]

Oil temp and Coolant temp are different.

America is #1 consumer of oil in the world and improving fuel economy is a necessity.

 

[OVERKILL]

Originally Posted By: CATERHAM

But remember the engineers have of course factored this all in to the lightest grade they recommend.


Or as part of their OEM testing and approval regimen if an approval is called for.

 

[IndyIan]

Originally Posted By: OVERKILL
Originally Posted By: CATERHAM

But remember the engineers have of course factored this all in to the lightest grade they recommend.


Or as part of their OEM testing and approval regimen if an approval is called for.

I imagine they leave a significant safety margin, but it would be interesting to run the average 10 year old, 160k car through the same tests and see if the ideal oil is still a 5W20? Maybe add a rich fuel condition brought on by a marginal O2 sensor?
It probably doesn't hurt at that point to go to 5W30 instead of a 5W20 if you are going to be towing or running the motor harder than normal.

 

[Shannow]

Manufacturers know what they are doing, and do oodles of research, such as the chart attached, produced by Honda.

It's a map of the percentile of vehicle usage patterns, and as can be seen, the "average" US utilisation of engine perfromance envelope is quite conservative, when compared to their analysis of European vehicles.

Thus they can with high confidence spec a "1 grade fits all" for the US market, and throw in a couple of disclaimers for the outlying vehicle users.

Europeans, it trends have a more disparate useage of revs and load...different oil specced.

As to temperature and ambient, my L67 oil temperature after 20km on the highway is 105-109C, higher than coolant...even at 5c...drop it into "2", 4,000RPM for 10 mins, and it's 129-135C...same speed, same hp applied to the rear wheels...apply those findings to the Honda chart, and you can see that 5W20 and my L67 wouldn't be a good combinations.

 

[Quattro Pete]

Thanks for that chart, Shannow!

 

[Trav]

So much for running XW20 in vehicles operated at high revs or loads.
Just like the Toyota 86 that specs 10w60 for track use. Caterhams tilt light went off on that one even with the OE manual as proof.

 

[dlundblad]

Originally Posted By: KrisZ
Originally Posted By: dlundblad
I asked this before, but didnt get a straight answer.



Well, since the industry stopped using straight weight oils long time ago, why would you expect to get a straight answer?


You caught it!!!

 

[dlundblad]

What sort of driving conditions do Australians see that require such a thicker weight then?

Autobahn users I can understand (High RPM's), but Australia? Its just super hot right? I am not aware of any autobahn like driving.. Never been to Australia though either.

 

[mjoekingz28]

Originally Posted By: dlundblad
I asked this before, but didnt get a straight answer.

Whats the point of running a thicker running weight in extreme heat? We see here that (some) Australians and folks in the Middle East like a 50 or 60 weight oil. Wouldn't the radiator keep oil temperature somewhat in check and prevent any oil related failures? I would also think an oil cooler would be a standard option for vehicles in these regions. We also see engines that spec a much thicker weight in Europe and the other mentioned regions while the identical US version will take a 20 or 30 weight oil. (It has been mentioned here that a European car's severe use yields a thicker oil.. high autobahn speeds for example?)

I don't understand the reason behind any of this. In the US, thin seems to be in while other places are still using a thicker oil.

The question is why do old cars and some specific models request you change viscosity to correlate with ambient temp,,,,while, some modern models spec, say 5w-20 for all temps possible?

 

[Merkava_4]

Originally Posted By: dlundblad
I asked this before, but didnt get a straight answer.


Forget about temperature for awhile and just think about viscosity.

Question:
What happens when you lubricate a bar clamp with oil that's too thick?

Answer:
The oil peels off the threads before going through the tunnel, therefore leaving the threads dry.

Question:
What happens when you lubricate a bar clamp with oil that's too thin?

Answer:
The oil goes through the tunnel, but doesn't fill up the space between the threads and the tunnel.

From my experience, the oil that makes the bar clamp handle turn the easiest is the oil that's able to fit through the tunnel AND fill up all the space between the threads and the tunnel.

That's my explanation of how the correct viscosity lubricates the best.

Not near as fancy as Shannow's explanation with all the colorful display graphs and other fluffy stuff, but it makes sense to me.