Help me understand severe service

[iExcel]

OK. I'm reading what's posted at Frequently Asked Questions (FAQ) About The 3000 Mile Oil Change Myth and the following conditions are considered severe.

• Extensive idling or in stop-and-go traffic.
• Cold weather, less than 10 degrees.
• Extreme heat, more than 90 degrees.
• Extreme humidity.
• Repeated short-distance trips of less than five miles.
• Towing a trailer or hauling heavy materials.

I can understand most conditions except for the ones related to ambient temperatures. For low temperature, the oil flows not as easily and thus it could impose damage to the engine. Why does low temperature shorten the service life of the oil as well? The additives are being consumed faster starting from a low temperature?

The same for the hot temperature, I mean an engine's operating temperature is around 200F, which is much higher than the ambient temperature we can live with. So, why does a high temperature result in shorter oil life,? I think if the cooling system runs properly, this shouldn't be a concern.

 

[StevieC]

This is a blanket statement IMO to cover extreme temperatures that could cause the oil to never reach full operating temperature because it's so darn cold outside and this will cause acidity in the oil from the engine running richer and causing more engine by-product.

In the extreme heat it can cause the engine oil to break-down and/or shear in weight which can then lead to deposits/sludge.

For an engine to operate efficiently and the oil to have a long life there is a happy-medium set of conditions that must be met.

 

[iExcel]

Originally Posted By: StevieC
This is a blanket statement IMO to cover extreme temperatures that could cause the oil to never reach full operating temperature because it's so darn cold outside and this will cause acidity in the oil.

So, if the oil has a chance to warm up to the operating temp, no matter how cold outside is, it shouldn't shorten the life of the oil. Right?

Originally Posted By: StevieC

In the extreme heat it can cause the engine oil to break-down and/or shear in weight which can then lead to deposits/sludge.

But the temperature you refer to here is the engine oil temp not the ambient temp, isn't it?

 

[StevieC]

I would say yes assuming that all the other systems are functioning properly and vehicle is well maintained and it's fuel injection/emissions from the last 10 years or more current the it should not in anyway shorten the oil life if the oil reaches operating temperature. Even if driving in Alaska, so long as said conditions above are met.

As for point 2, yes but the ambient temperature makes it very difficult for and engine to cool itself adequately while it is surrounded by 100F heat and sticky humidity and has a load (you and passengers and weight of the vehicle) it is carrying and you probably with the A/C on.

 

[d00df00d]

Originally Posted By: iExcel
For low temperature, the oil flows not as easily and thus it could impose damage to the engine. Why does low temperature shorten the service life of the oil as well? The additives are being consumed faster starting from a low temperature?

Condensation builds up when the car sits in the cold. Also, the engine runs less efficiently and generates more contaminants (unburned fuel, by-products, etc.), although this is becoming less and less of an issue with modern cars.


Originally Posted By: iExcel
The same for the hot temperature, I mean an engine's operating temperature is around 200F, which is much higher than the ambient temperature we can live with. So, why does a high temperature result in shorter oil life,? I think if the cooling system runs properly, this shouldn't be a concern.

Your cooling system actively pumps heat out, so it can regulate its temperature pretty well. Your oil can't do that. In most cars, the only "cooling" it has is the air blowing across the bottom of the oil pan. Thus, oil temps will be significantly hotter in warmer weather.

Also, remember the wording in the FAQ: "Extreme heat, more than 90 degrees." Depending on the car and how it's being used, that might start to stress even a fully working cooling system.

 

[iExcel]

Originally Posted By: StevieC

As for point 2, yes but the ambient temperature makes it very difficult for and engine to cool itself adequately while it is surrounded by 100F heat and sticky humidity and has a load (you and passengers and weight of the vehicle) it is carrying and you probably with the A/C on.
but the oil is operating at 200F while the ambient temp is 100F, still 100F difference. The heat can still be transferred from the 200F engine to the 100F coolant. As long as the temp diff is there, the oil will never go higher than 200F, which doesn't really matter to the life of the oil. I mean the oil is already happily working under 200F, why is the 100F ambient temp a concern? The ambient 100F doesn't add more heat to the 200F oil temp as heat doesn't go from a low temp to a high temp.

 

[iExcel]

Thanks. That makes sense.

 

[ZZman]

Engines work best at their normal operating temp.

Cold weather can shorten oil life by allowing condensation/acids to build up in the oil.

 

[StevieC]

While you are doing 1500 RPM or more the problem is when you are idling and the oil isn't circulating and hot sitting in the pan and the engines parts that aren't efficiently cooled by the coolant are heating up and waiting for more cool oil to help keep them cool.

 

[mechanicx]

Originally Posted By: iExcel
Originally Posted By: StevieC

As for point 2, yes but the ambient temperature makes it very difficult for and engine to cool itself adequately while it is surrounded by 100F heat and sticky humidity and has a load (you and passengers and weight of the vehicle) it is carrying and you probably with the A/C on.
but the oil is operating at 200F while the ambient temp is 100F, still 100F difference. The heat can still be transferred from the 200F engine to the 100F coolant. As long as the temp diff is there, the oil will never go higher than 200F, which doesn't really matter to the life of the oil. I mean the oil is already happily working under 200F, why is the 100F ambient temp a concern? The ambient 100F doesn't add more heat to the 200F oil temp as heat doesn't go from a low temp to a high temp.


I think in the Winter while the average coolant temperature might be 195F the sump can be several degrees cooler that it would be in the Summer. In high speed driving in 90+ F it's not uncommon the coolant temp to rise despite what the dash guage says and for oil consumption to go up quite abit. The oil is being oxidized and contaminates are being left behind that the oil filter doesn't entirely remove. I think cold weather driving is worse on oil of the two. Fuel enrichment contaminates and sheers the oil, plus it takes longer for the oil to get to best operating temperature.

 

[StevieC]

Short trips in cold weather yes... Oil that reaches operating temperature in cold weather is perfectly fine IMO.

 

[mechanicx]

It is better but the oil is still exposed to cold enrichment fuel sheering and a slower warm up. Plus the oil may not ever get all that hot for long enough. It all depends on how many cold starts it does and how long it gets ran on at operating temp.

 

[Gene K]

1. Continuous Short Trips in which the vehicle is never allowed to reach full operating temperature.

2. Continuous operation in arctic conditions.

3. Extended Idle such as Taxi, Police, or Livery Service.

4. Extreme Hot Temps such as Saharan Africa while using lubricants equivalent of API SK or Worse. If you use SL or better you can use normal schedule.

Thats the Ford version of Severe Service.

 

[dparm]

^ I tend to agree with that more.

These are total [censored] and apply to basically any car:

-Extensive idling or in stop-and-go traffic.
Short of living in the middle of nowhere and never idling the car, every car does this a decent amount.

-Cold weather, less than 10 degrees.
A good portion of the US sees these temps. Not daily, but fairly often. There were at least 10 days in Chicago's latest winter that were like this.

-Extreme heat, more than 90 degrees.
Again, most cars will see this unless you live somewhere very mild. Chicago has already had several 90+ days and it's only mid-July.

-Extreme humidity
Not sure what "extreme" is, but plenty of US residents live in humid climates. Again I cite Chicago as the example: it was 92 degrees with 85% humidity yesterday. That's normal.



It's the towing, not reaching operating temperature, and truly extreme temps (below zero and over 100) that will be heavy-duty.