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Oil temperature.

gtx3076

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#1
Cruising at 70+ my oil temps stay above 200*. Once I slow down they begin to drop and they can get down to 170-180 idling after a drive. Any input on this? Big deal? Not really?

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#2
I've seen my oil temperatures rise to 2:30 on really hot days so I'd say you're probably in the ballpark also remember these cars don't have a dedicated oil sensor I believe it's based off a calculation on coolant temperature as well.
 


SteveS

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#3
If your car were only getting oil temp to 200, there would be something wrong with it. Below 220 degrees, water, gasoline, and other impurities won't boil out, causing acid impurities to build up. The ideal is to keep oil between 230 and 260 degrees. Conventional mineral oil starts to break down at 275 degrees while full synthetic oils like you should be using in the Fiesta ST withstand 300-plus degrees before breaking down.
 


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gtx3076

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Thread Starter #4
If your car were only getting oil temp to 200, there would be something wrong with it. Below 220 degrees, water, gasoline, and other impurities won't boil out, causing acid impurities to build up. The ideal is to keep oil between 230 and 260 degrees. Conventional mineral oil starts to break down at 275 degrees while full synthetic oils like you should be using in the Fiesta ST withstand 300-plus degrees before breaking down.
Damn I don't think I've ever seen the oil get up that high even in 100+ degree weather here in Texas.

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#5
If your car were only getting oil temp to 200, there would be something wrong with it. Below 220 degrees, water, gasoline, and other impurities won't boil out, causing acid impurities to build up. The ideal is to keep oil between 230 and 260 degrees. Conventional mineral oil starts to break down at 275 degrees while full synthetic oils like you should be using in the Fiesta ST withstand 300-plus degrees before breaking down.
Actual studies have shown that 90 C (194 F) is the point at which that happens. There's a good read on it by a mechanical engineering journal here.
 


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#6
I've seen my oil temperatures rise to 2:30 on really hot days so I'd say you're probably in the ballpark also remember these cars don't have a dedicated oil sensor I believe it's based off a calculation on coolant temperature as well.
I second this - our cars do not have a dedicated oil temperature sensor from the factor and I believe the calculation is a culmination of coolant, ambient, and a few other sensors. The lack of quantitative data on this makes it a subject full of opinions. Plus every person has a unique opinion on what ideal oil temps are. I was trolled into a 30 post feud a while back.
View: https://media.giphy.com/media/MxH83SEztdtao/giphy.gif
 


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SteveS

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#8
Actual studies have shown that 90 C (194 F) is the point at which that happens. There's a good read on it by a mechanical engineering journal here.
That paper has nothing to do with evaporating water and other contaminants out of oil. It is about separating a sunflower oil and water emulsion into separate oil and water phases using electrostatic charge and compares it to heating to 90 degrees Celsius. In the end, though they are separating oil and water, they don't get rid of the water. Water boils at 212 degrees, and therefore temperatures must exceed that temperature in order to get rid of water from automotive oil, particularly since automotive oil has detergents in it which are meant to capture the water and hold onto it. Engine oil routinely sees temperatures far in excess of the boiling point of water, and when it doesn't, such as taking only short trips in cold weather where the engine never fully warms up, will result in buildup of acidic sulfur compounds, sludging, etc. from the water which condenses in the oil pan remaining in the oil because it's never boiled out.

Just like the with the guy who maintained that his accessport told him his charge air temperature was measured below ambient, the situation is not one of the Fiesta ST defying the laws of physics, but rather an inaccurate measurement being reported by the accessport.
 


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#9
Water boils at 212 degrees, and therefore temperatures must exceed that temperature in order to get rid of water from automotive oil, particularly since automotive oil has detergents in it which are meant to capture the water and hold onto it.
Sort of, water boils at 212 degrees F at sea level. But water's boiling temperature is highly dependent on atmospheric pressure. I think water boils ~200 degrees F at ~6,250' MSL. Below boiling, water can evaporate at much lower temperatures to varying degrees. Water in its solid form (frozen) can even evaporate at very slow rates.

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#12
That paper has nothing to do with evaporating water and other contaminants out of oil. It is about separating a sunflower oil and water emulsion into separate oil and water phases using electrostatic charge and compares it to heating to 90 degrees Celsius. In the end, though they are separating oil and water, they don't get rid of the water. Water boils at 212 degrees, and therefore temperatures must exceed that temperature in order to get rid of water from automotive oil, particularly since automotive oil has detergents in it which are meant to capture the water and hold onto it. Engine oil routinely sees temperatures far in excess of the boiling point of water, and when it doesn't, such as taking only short trips in cold weather where the engine never fully warms up, will result in buildup of acidic sulfur compounds, sludging, etc. from the water which condenses in the oil pan remaining in the oil because it's never boiled out.

Just like the with the guy who maintained that his accessport told him his charge air temperature was measured below ambient, the situation is not one of the Fiesta ST defying the laws of physics, but rather an inaccurate measurement being reported by the accessport.
Right, and heating it to 90 C provided good separation, which in the case of a car would allow the PCV system to do its job more effectively. When that vented water/gasoline gets cycled back in to the intake, it should evaporate or combust in the combustion chamber. It's not all about boiling or evaporating the water while in the oil (though that does work even better), it's just about separating it from the oil. I'll give you that sunflower oil isn't a perfect 1:1 comparison with automotive oil, so there may be some variance there. But if oil really did need to be 220F to provide a good "cleansing", I'd expect to see 240 and 250 F as normal sustained oil temps (my '19 Golf R, which did have an actual oil temp sensor, liked to run around 210-220F, with 230F seen during highway cruising).
 


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gtx3076

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Thread Starter #13
I have an external oil temp and pressure sensor, and I see legitimate oil temps in the 230 range.
I'm probably fine them. I never monitored it until recently. Does take more driving than I thought to even match reported coolant temps.

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#14
I'm probably fine them. I never monitored it until recently. Does take more driving than I thought to even match reported coolant temps.Sent from my SM-G930T using Tapatalk
Agreed and same here. Oil temp is one of the normal metrics I have up and it usually takes ~20-30mins for me to see similar temps on oil and coolant through the APv3. The only time I see the reported oil temp go above coolant temps is on the highway (which makes sense to me).
 


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#15
Anyway, unless you all have separate oil gauges with a sender, all your oil temps displayed on the AP are theoretical since it's calculated with an algorithm and not with an oil temp sender.
 


TemecFist

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#16
Anyway, unless you all have separate oil gauges with a sender, all your oil temps displayed on the AP are theoretical since it's calculated with an algorithm and not with an oil temp sender.
Yep, my oil temp and pressure gauge is completely stand alone. No AP.
 


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#17
Mine stays around 190. It stays around 220-230 when pulling a trailer with my motorcycle on the back. Been debating on getting a larger radiator or oil cooler for the trailer days. We’ll see how a larger turbo affects this.


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SteveS

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#18
Right, and heating it to 90 C provided good separation, which in the case of a car would allow the PCV system to do its job more effectively. When that vented water/gasoline gets cycled back in to the intake, it should evaporate or combust in the combustion chamber. It's not all about boiling or evaporating the water while in the oil (though that does work even better), it's just about separating it from the oil. I'll give you that sunflower oil isn't a perfect 1:1 comparison with automotive oil, so there may be some variance there. But if oil really did need to be 220F to provide a good "cleansing", I'd expect to see 240 and 250 F as normal sustained oil temps (my '19 Golf R, which did have an actual oil temp sensor, liked to run around 210-220F, with 230F seen during highway cruising).
Which is exactly what it needed to be. That's why cars which do extensive stop and go/idling service have to follow the heavy duty service intervals on oil changes, while cars that see highway use follow the light duty service intervals. The time in the 220-230 temps is getting in the optimal range for oil longevity. I think you are misinterpreting my post, which was to say that unlike coolant temps, you want the oil to be hotter than water boiling temperatures a significant portion of the time. And even the strangely vociferous support for low coolant temperatures on this forum is somewhat misplaced. Sure, you don't want to overheat the engine, but people seem to believe that if their engine goes above 190 degree coolant temperature they are going to blow up their engine or something. In fact, overcooling the engine isn't good for it either.
I think people get an accessport and become obssessed with watching numbers. In this case (Fiesta ST), it's a number that's not even real.

By the way, the temperatures I quoted were not my own; they came from automotive information websites. But I've been an automotive enthusiast for longer than most of you have been alive, and it's the same as it's always been.
 


Hypergram

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#19
Cruising at 70+ my oil temps stay above 200*. Once I slow down they begin to drop and they can get down to 170-180 idling after a drive. Any input on this? Big deal? Not really?

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To put it simply, your oil temps are fine. Highest I've ever seen (on the AP monitor) are 238 degrees in 104 degree weather going about 80-85 on the highway. If you think you're oil and coolant temps are too high, blast the A/C on hot and watch them drop.
 


M-Sport fan

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#20
I have an external oil temp and pressure sensor, and I see legitimate oil temps in the 230 range.
Have you ever run the oil 'gauge' function on the AP at the same time as the dedicated REAL oil temp gauge to see just how far off the interpolated/calculated figures for oil temp are on the AP from the actual temps??
(Or don't you even own an AP in order to do the above?)
 


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