Thermal Break Down

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I drive a 2004 F250 6.0 Powerstroke using Motorcraft 15w40 oil (5000 mile change interval) with motorcraft filters and recently went on a trip towing about 7000lbs my oil temps spiked at 252 with ambient temps of about 92 F, unloaded I usually run around 20 degree deltas. Last winter i had my coolant system flushed new Motor Craft oil cooler installed with new red Rotella anti freeze, coolant filter, etc. I can not afford to do this procedure again so now I am looking for the breakdown temps of diesel rated motor oils for my next change. Does anyone have access to this information. As a bonus anyone have any ideas as to why my temps spiked?
 
252F is only 122C, nothing to really worry about as a spike. NOACK is tested at 150C (302F) for an hour. Oil flashpoints are usually well over 200C (392F).
Were you towing up steep grades while running the AC?
I've hit over 230F in my little SUV with just my family and a load of softball gear in the Monadnocks in the mid 90s. Thicker oils will tend to run hotter, you could probably run a bit cooler with a HD 10w30 but the oil film thickness will still be greater with the 15W40 under the same conditions even if the latter oil is a bit hotter.
 
Originally Posted By: Virtus_Probi
252F is only 122C, nothing to really worry about as a spike. NOACK is tested at 150C (302F) for an hour. Oil flashpoints are usually well over 200C (392F).
Were you towing up steep grades while running the AC?
I've hit over 230F in my little SUV with just my family and a load of softball gear in the Monadnocks in the mid 90s. Thicker oils will tend to run hotter, you could probably run a bit cooler with a HD 10w30 but the oil film thickness will still be greater with the 15W40 under the same conditions even if the latter oil is a bit hotter.


My oil temps stayed pretty steady in the 250 area for a long time under throttle. However when I was idling the temps came down to a lower level fairly quickly. Yes we were using the AC and running about 75 mph on the interstate through KY.
 
If I was hitting 250, I'd switch to a synthetic as they have higher thermal breakdown temps.
 
Originally Posted By: sfloyd33
Originally Posted By: Virtus_Probi
252F is only 122C, nothing to really worry about as a spike. NOACK is tested at 150C (302F) for an hour. Oil flashpoints are usually well over 200C (392F).
Were you towing up steep grades while running the AC?
I've hit over 230F in my little SUV with just my family and a load of softball gear in the Monadnocks in the mid 90s. Thicker oils will tend to run hotter, you could probably run a bit cooler with a HD 10w30 but the oil film thickness will still be greater with the 15W40 under the same conditions even if the latter oil is a bit hotter.


My oil temps stayed pretty steady in the 250 area for a long time under throttle. However when I was idling the temps came down to a lower level fairly quickly. Yes we were using the AC and running about 75 mph on the interstate through KY.


I'm not sure if it's current, but I found a PDS for Motorcraft 15W40 that claimed a 441F flashpoint (it paired that with 277C, must have been a typo as 441F=227C). I know you're not worried about your oil catching fire, but that number suggests to me that your oil can handle 250F for some time. I wasn't able to find NOACK loss for that oil, but that test is not a good direct comparison for engine use because the sample has a constant air flow over it to immediately carry away anything that vaporizes.

Did you happen to notice any unusual oil consumption due to your trip? If you did, maybe it would be worth looking at an oil that is especially robust at high temps. It not might be a good match for your application and tends to be expensive, but M1 5W30 ESP (Euro diesel oil) has a low NOACK loss of around 6% and a very high 254C (489F) flashpoint. Its 3.58 HTHS is very close to some XW40 oils, M1 0W40 FS is around 3.6.
 
I don't think you need to worry about the 250-ish temps. I give dnewton3 credit for easing my mind a few years ago when I had similar oil temps in my big Volvos.

I had two Volvo class 8 trucks (D13 engines) that were programmed to run higher oil temps than any other truck engine I had owned/driven before. The oil cooler would only cool the oil to 239F and let it go to 247 or so before cooling again. On longer pulls in high ambient temps, the oil temp would remain around 250, and over the course of an oci, it added up to hours spent at 250.

I posted a few UOAs that showed that the oil held up fine, in that they didn't oxidize into a mess. The viscosity was in good shape regardless of the oil. I used Rotella, Delo and Kendall 15W40 and Delvac Elite 10W30 and they all handled it fine, as did the engines.
 
You have a 6.0, oil temps are extremely critical, no worries about the oil but if you are still seeing a 20F delta you oil cooler is partially clogged.
The 6.0 oil cooler test is 65 mph unloaded and relatively flat ground, your delta should be no more than 10F with a new cooler, with 15F acceptable. If you are seeing a 20F delta towing this is also acceptable and your 252F temp is normal.

I was in the seat of a 6.0 for 12 years and never experienced an engine issue, I know not the norm. On my '07 I made the switch to 10w-30 and never looked back. UOA every OC at 7,500 mi. and they were all exceptional with my last one going 215,000 mi. before trading it in on my current 6.7 because of rust issues not mechanical.
My advice to you is to install a coolant filter asap as the setup on a 6.0 the oil cooler acts as the coolant filter, as you have already discovered.
Try a 10w-30, I never had an issue and all of my UOA's are posted in the HDEO section on here.

A synthetic oil is not needed in your application as I proved that already with my two 6.0's.
 
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252 degrees is nothing for motor oil, Not even a concern. Even short bursts up to 300.
Small concern if you start running 275+ on a regular basis.

But yes, nothing wrong with doing some research. Some oils will be better then others at extremes but 252 is not in any way an extreme.
 
The thing that is kicking me in the butt is that I installed a new Motorcraft oil cooler less than a year ago along with a very good Extended Life Coolant and filter. I have a Insight CTS 2 electronic gauge setup and that is what I am going off of for my oil temps. Does anyone think it possible that this gauge is lying to me and if so how would i tell?
 
Originally Posted By: sfloyd33
The thing that is kicking me in the butt is that I installed a new Motorcraft oil cooler less than a year ago along with a very good Extended Life Coolant and filter. I have a Insight CTS 2 electronic gauge setup and that is what I am going off of for my oil temps. Does anyone think it possible that this gauge is lying to me and if so how would i tell?


Have you run the test as I described in the previous post to determine if you are within spec or not?

Your gauge is reading what the engines computer is telling it, as long as your monitor is programmed properly is reading properly.

I don't want to alarm you but its very possible your new oil cooler is clogged as it happened to thousands of others who replaced the oil cooler and didn't completely/effectively flush the cooling system.
First verify if your monitor is reading correctly and preform the test as I described before jumping to conclusions, as I said earlier if your delta is 20F while towing thats completely normal.
 
Just one other note to the OP about "thermal breakdown" as others including myself said 250 degrees for motoroil is nothing.
But as far as facts go, if you research you will find out that API SN oil requires any oil rated SN to pass a ONE HUNDRED HOUR sequence test at 300 degrees F.
Im just saying that to give support to the statements in here that 250 degrees is nothing, you can even look further and I think you will see the same for any C only rated oil.
 
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