Hot ambient temps and engine oil question.
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gathermewool
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Not every car has an oil cooler, so the oil cycles through the pan has less time to cool. Excessive high load operation might cause the oil to shear and either accelerate its degradation or accelerated engine wear.
Even with an oil cooler, lower ambient temps would provide a larger delta to cool the oil more efficiently. My STI has an oil to coolant heat exchanger, so it doesn't really matter much, except that both the oil and coolant might spend more time at the higher end of the operating temperature band during really hot days.
For most drivers, however, you're right; it doesn't matter.
Even with an oil cooler, lower ambient temps would provide a larger delta to cool the oil more efficiently. My STI has an oil to coolant heat exchanger, so it doesn't really matter much, except that both the oil and coolant might spend more time at the higher end of the operating temperature band during really hot days.
For most drivers, however, you're right; it doesn't matter.
It's been answered before but your right high ambient temp's are of course great on start-up.
In most applications today high ambient temp's won't significantly increase maximum oil temp's when the vehicle is moving.
In some applications, especially those with oil sumps exposed to air flow, higher ambient temp's with increase oil temp's but not dramatically so. It is the combination of high ambient temp's and lots of WOT that will maximize oil temp's. But if you're racing around or towing a heavy load through the mountains, ambient temp's won't significantly raise oil temp's.
In most applications today high ambient temp's won't significantly increase maximum oil temp's when the vehicle is moving.
In some applications, especially those with oil sumps exposed to air flow, higher ambient temp's with increase oil temp's but not dramatically so. It is the combination of high ambient temp's and lots of WOT that will maximize oil temp's. But if you're racing around or towing a heavy load through the mountains, ambient temp's won't significantly raise oil temp's.
They only effect starting unless its air cooled.
I look at it this way, the sooner the oil reaches optimal operating temps the better it is for the engine. 100F is going to get the oil to operating temps a lot faster than 0F will. I'll go under the assumption there are no problems with the engine, otherwise all bets are off.
40F ambient is considered a cold weather start here in Phoenix. Unfortunately my Outlander doesn't provide oil temp to my ScanGauge II, but coolant temp when totally warmed up runs between 186-195F.
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The road pavement where I live in incredibly hot. Frying an egg on it is not a joke. My 2006 Honda's oil pan sits 4.7 in. off it (I think).
The radient heat off the road is relentless, and although there is no way to scientifically prove it, I imnagine there is some degree of thermal degradation occouring if the oil never really cools off during the day. It's like being parked next to a heater for 6+ months. JMO.
The radient heat off the road is relentless, and although there is no way to scientifically prove it, I imnagine there is some degree of thermal degradation occouring if the oil never really cools off during the day. It's like being parked next to a heater for 6+ months. JMO.
Originally Posted By: gfh77665
The road pavement where I live in incredibly hot. Frying an egg on it is not a joke. My 2006 Honda's oil pan sits 4.7 in. off it (I think).
The radient heat off the road is relentless, and although there is no way to scientifically prove it, I imnagine there is some degree of thermal degradation occouring if the oil never really cools off during the day. It's like being parked next to a heater for 6+ months. JMO.
My exhaust pipe passes about 1.25 inches below my oil pan. Others have pre-cats that get even more scalding.
The road pavement where I live in incredibly hot. Frying an egg on it is not a joke. My 2006 Honda's oil pan sits 4.7 in. off it (I think).
The radient heat off the road is relentless, and although there is no way to scientifically prove it, I imnagine there is some degree of thermal degradation occouring if the oil never really cools off during the day. It's like being parked next to a heater for 6+ months. JMO.
My exhaust pipe passes about 1.25 inches below my oil pan. Others have pre-cats that get even more scalding.
Yeah, as Mr. Haas says in Motor Oil University on this site (first thing I read when I joined recently), most modern cars' cooling systems are designed to keep the engine at 212 deg when fully warmed up, and the oil with it. Manufacturers' oil specs are spec'd for this operating temp for proper viscosity. The cooler the ambient temp while the engine is off, the worse it is for the engine at startup. The oil is more like honey and can't flow to the vital engine parts.
I do not consider 100F ambient temperature hot nor do I consider good reason change to a higher oil grade. But do not tell someone from Texas this because for some reason it is hotter and harsher in Texas compared to the rest of the country.
Yep, like Arizona is way colder.
Aussies and Texans love their 40 grades.
Would it start another civil war if the rest of the States started to refer to Texas as down under?
Would it start another civil war if the rest of the States started to refer to Texas as down under?
Yeah I wish I could brag and say where I am is the hottest part of the country, oh wait not really. But that title belongs to Death Valley, now that place is hot! Texans believe they are in the Republic of Texas anyways the rest of the Union just lets them believe that it is not worth the hassle.
Originally Posted By: volk06
Why do people think or consider 100F ambient temp is hard on oil? Flows easier in the engine than colder temps. If engines run at 180-210F how can 100F ambient temprature be hard on the oil and be considered severe service?
Easy-peezy:
Because that 100 deg F starting temp means it is just that much warmer at running temps [warmer than 25 deg F ambient temps,let's say]
[Not an insurmountable situation, but a legit reason to note ambient temps as a very real factor ]
Why do people think or consider 100F ambient temp is hard on oil? Flows easier in the engine than colder temps. If engines run at 180-210F how can 100F ambient temprature be hard on the oil and be considered severe service?
Easy-peezy:
Because that 100 deg F starting temp means it is just that much warmer at running temps [warmer than 25 deg F ambient temps,let's say]
[Not an insurmountable situation, but a legit reason to note ambient temps as a very real factor ]
Ambient temperatures certainly are a real factor, but, as you're aware, people do exaggerate. Our hottest days are around 40 C, and our coldest days are -40 C. That's an 80 degree Celsius spread. The sump operating temperature doesn't vary by 80 degrees. The average engine at 40 C needs a 40 or 50 grade about as much as I need Imperial Oil to formulate a straight 0W for me for winter.
In the Audi, with a good oil temperature gauge and a functioning, thermostatically controlled oil cooler, I noticed a few degrees difference between winter and summer sump temperatures. I think a 10 degree difference would be stretching it in that car.
In the Audi, with a good oil temperature gauge and a functioning, thermostatically controlled oil cooler, I noticed a few degrees difference between winter and summer sump temperatures. I think a 10 degree difference would be stretching it in that car.
I have found there is a 10-20 degree variation operating temperatures on oil in the sump between winter temps 25F ambient temperature and 120F summer ambient temperatures. The biggest factor ambient temperatures have will be heating and cooling the oil after shutdown.
Yep, degrees Celsius are larger than degrees Fahrenheit, so you're experience is similar to what I'd see in mine, though I routinely saw much colder than 25 F. Heck, at 25 F, the Audi called for 15w40. As far as cold starts go, my Audi then (and my G now) was stored in a heated garage all winter, so a -40 C start with the sump actually at that temperature was extremely rare.
Originally Posted By: mechtech2
Originally Posted By: volk06
Why do people think or consider 100F ambient temp is hard on oil? Flows easier in the engine than colder temps. If engines run at 180-210F how can 100F ambient temprature be hard on the oil and be considered severe service?
Easy-peezy:
Because that 100 deg F starting temp means it is just that much warmer at running temps [warmer than 25 deg F ambient temps,let's say]
[Not an insurmountable situation, but a legit reason to note ambient temps as a very real factor ]
If an engine reaches operatIng temperature how is it that much higher? Whether its 40f or 100f ambient, 210f at operating is still the same.
Originally Posted By: volk06
Why do people think or consider 100F ambient temp is hard on oil? Flows easier in the engine than colder temps. If engines run at 180-210F how can 100F ambient temprature be hard on the oil and be considered severe service?
Easy-peezy:
Because that 100 deg F starting temp means it is just that much warmer at running temps [warmer than 25 deg F ambient temps,let's say]
[Not an insurmountable situation, but a legit reason to note ambient temps as a very real factor ]
If an engine reaches operatIng temperature how is it that much higher? Whether its 40f or 100f ambient, 210f at operating is still the same.
Originally Posted By: CATERHAM
It's been answered before but your right high ambient temp's are of course great on start-up.
In most applications today high ambient temp's won't significantly increase maximum oil temp's when the vehicle is moving.
In some applications, especially those with oil sumps exposed to air flow, higher ambient temp's with increase oil temp's but not dramatically so. It is the combination of high ambient temp's and lots of WOT that will maximize oil temp's. But if you're racing around or towing a heavy load through the mountains, ambient temp's won't significantly raise oil temp's.
Depends on what you mean is "significant", as there re various laws of physics that apply in the middle.
Radiative heat transfer has a power of T1^4-t2^4 function (in Kelvin), which is a very powerful means of moving heat...sit in a room with your front to a heater, and back to an open window at night.
Convection requires a simple delta T...heat moved is a function of the difference between the hot fluid and ambient...ambient temperature rises 5F, and the hot fluid rises at least 5F at equilibrium.
All of these discussions centre around the standard "maximising gains, minimising returns" type curve interaction.
Moving towards thinner oils, and in hotter temperatures is using up the safety margin that exists between asperite contact, asperite contact in x miles, and asperite boundary lubrication.
It's a risk/benefit analysis, and as I was ridiculed for before, an XW-20, dragging a trailer, and experiencing a coolant failure is closer to the margin than an XW-40.
High ambients increase oil temps...full stop.
Dangerously ?
Depends on the line that you are riding, and if you are in control of it !
It's been answered before but your right high ambient temp's are of course great on start-up.
In most applications today high ambient temp's won't significantly increase maximum oil temp's when the vehicle is moving.
In some applications, especially those with oil sumps exposed to air flow, higher ambient temp's with increase oil temp's but not dramatically so. It is the combination of high ambient temp's and lots of WOT that will maximize oil temp's. But if you're racing around or towing a heavy load through the mountains, ambient temp's won't significantly raise oil temp's.
Depends on what you mean is "significant", as there re various laws of physics that apply in the middle.
Radiative heat transfer has a power of T1^4-t2^4 function (in Kelvin), which is a very powerful means of moving heat...sit in a room with your front to a heater, and back to an open window at night.
Convection requires a simple delta T...heat moved is a function of the difference between the hot fluid and ambient...ambient temperature rises 5F, and the hot fluid rises at least 5F at equilibrium.
All of these discussions centre around the standard "maximising gains, minimising returns" type curve interaction.
Moving towards thinner oils, and in hotter temperatures is using up the safety margin that exists between asperite contact, asperite contact in x miles, and asperite boundary lubrication.
It's a risk/benefit analysis, and as I was ridiculed for before, an XW-20, dragging a trailer, and experiencing a coolant failure is closer to the margin than an XW-40.
High ambients increase oil temps...full stop.
Dangerously ?
Depends on the line that you are riding, and if you are in control of it !
100F in C is 37.7C. If I was asked 20 years ago, I would have said this is not very hot. When I used to live in Southern Russia, daily 35-40C was considered normal summer temperature. It was hot, but more than bearable even though most buildings did not have AC. Now I live in the US, and the 100F DOES feel very hot here.. I don't know why. Maybe it's the humidity.
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