Ambient vs OIl Temp vs Coolant Temp

[Jim Allen]

Just an observation to share:

Vehicle: '05 F150 5.4L V8

Situation: Rural roads, 50-60 mph, 28 mile run with few stops, some in town miles, followed by another 28 mile return.

Load: 600 pound payload each way.

Ambient: 28F

Stabilized Coolant Temp: 194F

Stabilized Oil Temp: 178F


There was some discussion earlier about ambient temps vs oil temps. The above numbers above contrast greatly with these from the exact same route taken in August. The difference would be a lesser load in the bed. To whit:

Ambient: 91F

Stabilized Coolant Temp: 208F

Stabilized Oil Temp: 199F

 

[Colt45ws]

So, Im guessing the lesser load was the December run?

 

[Jim Allen]

Just the opposite, Colton. I carry 500 pounds of tractor weights during the winter for traction and had some lumber in the truck to boot. In the summer, I was traveling empty. 600# in a truck designed for a 3000# payload isn't much, but I just wanted to make note of it. It might add a few degrees to the oil temp but I dang sure aren't going to unload it, as I think it made the point as is.

I just remembered some comments from posters that doubted whether ambient had any effect on stabilized oil temp and I guess I just want to counter that with some observations.

 

[McKittrick]

Does your truck have a 195 F thermostat? I think the 63 F cooler ambient has you running on thermostat control in winter and running wide open in summer. I have found similar things in my vehicles once I started using the ScanGauge.

The heat exchanger area should be sized to reject the heat under hottest expected conditions and once the temperature falls the engine will use the thermostat to maintain a minimum temperature.

Does the truck have an oil cooler?

Oil temperature may vary with ambient due to pan cooling, small effect I would think, and temperature of other internal components which is partly driven by coolant temperature a larger factor.

Interesting results, maybe others can report how their vehicles are doing. For me yesterday was over 80 F so not much change from summer here yet.

 

[tmorris1]

Originally Posted By: Colt45ws
So, Im guessing the lesser load was the December run?

Not according to what he wrote. Unless it was 91F in Dec.

 

[Jim Allen]

Originally Posted By: McKittrick
Does your truck have a 195 F thermostat? I think the 63 F cooler ambient has you running on thermostat control in winter and running wide open in summer. I have found similar things in my vehicles once I started using the ScanGauge.

The heat exchanger area should be sized to reject the heat under hottest expected conditions and once the temperature falls the engine will use the thermostat to maintain a minimum temperature.

Does the truck have an oil cooler?

Oil temperature may vary with ambient due to pan cooling, small effect I would think, and temperature of other internal components which is partly driven by coolant temperature a larger factor.

Interesting results, maybe others can report how their vehicles are doing. For me yesterday was over 80 F so not much change from summer here yet.



Yeah, I see the coolant temp jump around a bit in winter, as the t-stat operates. FYI, the newer 5.4L Ford do not have a "coolant" temp gauge built in. Both the EFI and the factory gauge interpret coolant temp from cylinder head temp sensors. I installed an actual coolant temp gauge.. with the sensor in the spot where they normally appear, right under the t-stat.

No oil cooler but the the engine holds 7 quarts.

 

[Silber Igel]

I think its spot on. The OT should be about the same as the WT when the thermostat is full open. Meaning a hot to warm day. On a cold day it should be somewhat below that. I'd not worry about it a tiny bit.

 

[Colt45ws]

Interesting, even loaded (however lightly) with that low of an ambient the temperature delta was almost double that of in the summer with no load.
I agree that ambient cooling of the pan probably has little effect.
With the coolant at a higher temperature it must not be able to dump heat as efficiently. I suspect that at some point (probably under overheat conditions) it may even cross over, with the oil running hotter than coolant.
Wonder what would happen if you ran this with the radiator partially blocked to increase coolant temperatures closer to where they were in summer.
Im running about 80% blocked to get a stable CHT of 196F. With out the block I run 190F with some variation 188-192.
WT runs about 1-2F below CHT, I have found.

 

[Jim Allen]

Hmm? I haven't observed CHT since I installed the coolant temp gauge. Maybe I'll reprogram the Gryphon to show CHT for a while to compare.

Maybe I should block the radiator but I haven't yet. I have done so on my old FOrd diesel, because it takes forever to warm up on cold days.

 

[JOD]

Interesting--thanks for posting!

I have to say this must be car-dependent. Since we had that discussion before, I've been logging some data as well but have been to lazy to post, so here are my observations from last summer from a mixed city/highway drive, Ford Freestyle/Duratec 3.0, CFT-30 transmission:

92F ambient temp, stock thermostat (180?):

-coolant temp: 89C

-oil temp: 87C

94F ambient temp, 190 degree thermostat (after coolant exchange)

-coolant temp: 91C

-oil temp: 89C

18F ambient temp:

-coolant temp: 89C

-oil temp: 88C

45 ambient temp:

-coolant 91C

-oil temp 89C

What I noticed was that in the really cold temps (for me), at highway speeds coolant temp would fluctuate down a little more--but the averages were close. I didn't notice a real difference in moderate temps versus very hot.

These were taken in mixed drives (city/highway) of 30 minutes, averaged over the duration. The 94 degree day is at about 3,000 ft of altitude, but similar terrain. I have noticed that driving over an decent size mountain pass with a car loaded with gear in high ambient temps, coolant temp will rise as high as 97C. I've never seen it higher than that.

I guess the lesson here is that if you plan on altering your oil viscosity for seasonal temps, you better have a way to measure your oil temperature. I wonder why the difference? One additional thing to mention is that this car typically revs in the 1.5-2K range, due to the one speed transmission. I don't know if that's a factor or not, but I figure it's worth mention

 

[Jim Allen]

I'm sure it's vehicle dependent to a degree... maybe to a large degree. A truck has to have a large reserve of cooling capacity. A car, a crossover or a minivan, doesn't, as much.

How much oil does the Duratec hold? Does it have an oil cooler of any type?

Overall, a higher oil temp (within limits ) is better. An oil to water heat exchanger would balance the two temps nicely... helping the oil to warm up faster but also keeping it cooler as needed.

 

[JOD]

There's no oil cooler, and due to the very limited towing capacity (limited by the transmission), there's not much need for one, at least on this version. The 3.0L in some other applications does use one, but not mine.

The sump capacity it 6 qts, which seems like a lot for a 3.0L. I do wonder if the transmission has an effect, since the RPM's are consistently low on this vehicle.

I hear you on the oil temps--that was the reason I swapped the thermostat to a 190F. That said, from what I can see though the fill hole (which is quite a bit), the engine looked like new at 70K when I changed to the hotter t-stat.

 

[modularv8]

Originally Posted By: Jim Allen
Hmm? I haven't observed CHT since I installed the coolant temp gauge. Maybe I'll reprogram the Gryphon to show CHT for a while to compare.

Maybe I should block the radiator but I haven't yet. I have done so on my old FOrd diesel, because it takes forever to warm up on cold days.


Jim,

I believe your F150 comes has the "tow package" from a past discussion. In which case, it also has the heavy duty radiator and an external transmission fluid cooler up front. And if I remember correctly, it has a 30% greater heat rejection capacity over the standard equipped radiator.

 

[mechtech2]

The coolant temps should be more consistent.

An explanation could be that the summer temps overwhelmed your cooling system.
Also, maybe the winter ambient temps are causing overcooling.
Possibly the thermostat is aging and has changed it's operating characteristics.