What temperature is too hot for conventional oil?

[CarbonSteel]

I recently went through the mountain passes in southern California with the ambient air temperatures between 110F and 115F and through part of the Mojave desert with an ambient air temperature of 111F. Truck was loaded with four adults and a bed full of luggage and gear and I saw oil temperatures between 220F and 240F for extended times (I maintained speeds of 70+ the whole way). The oil temps would recover fairly quickly on the backsides of the mountains (down to 203F within 5 miles and the transmission temperature never went above 203F).

It did make me wonder what the temps would have been had I been towing. What would be considered the temperature limit for conventional CJ-4 oil? Can it handle 240F under sustained conditions? Any consideration for the turbo? I am (and have been) running either a synthetic 5W-40 or a SynBlend 15W-40. Thanks for your thoughts!

 

[demarpaint]

You're right about there. Conventional oil is probably going to start to break down at about 250F or so. Your bearing and turbo temps are probably a lot higher. The transmission temps are a bit high for my liking too.

I'd be using synthetic oil.

 

[Rand]

Its more the hottest the oil sees than the bulk oil temp.

I'd say you would benefit from a full syn if you do that trip often.

OTOH my forester sees 230-235F on the highway @80mph with A/C on full blast.

Towing at 65mph is similar if its a very hot day.

A/C on or off can be a difference of 10-20f

Mine is just the N/A FB25

 

[HemiHawk]

Originally Posted By: Rand
Its more the hottest the oil sees than the bulk oil temp.


Which in a turbo would be a quite a bit higher.

Out of curiosity what engine is this?

 

[CarbonSteel]

Originally Posted By: HemiHawk
Originally Posted By: Rand
Its more the hottest the oil sees than the bulk oil temp.
Which in a turbo would be a quite a bit higher. Out of curiosity what engine is this?
Not sure if you are asking me or Rand. But if me, it is my 6.7L Ford Powerstroke.

 

[mbacfp]

Great question and concern. I have the Cab & Chassis version of the Powerstroke 6.7 (F550 motorhome). One of my nagging aversions to trying conventional 10w-40 vs 5w-40 is driving in those occasional situations. In taking I-15 north to Las Vegas and going up those long grades with the temperatures over 105+...makes me feel better knowing Mobile Delvac 5w-40 is in the crank. However, those environments aren't the norm for me. I have seen those same temp ranges as 2015_PSD.

 

[HemiHawk]

Originally Posted By: 2015_PSD
Originally Posted By: HemiHawk
Originally Posted By: Rand
Its more the hottest the oil sees than the bulk oil temp.
Which in a turbo would be a quite a bit higher. Out of curiosity what engine is this?
Not sure if you are asking me or Rand. But if me, it is my 6.7L Ford Powerstroke.


Sorry that was for you sir. I was curious if there was an oil cooler. I know on my turbo car, the oil temp readings never really get too high, but I think its sampling after the cooler. Like Rand mentioned, the bulk temp on that run was high, but the temp in the hot spot (the turbo) will be much higher.

I have always seen that around 250F conventional will begin to break down, which again in a turbo would happen much quicker. On the other hand, I'm sure plenty of turbo cars in the past ran dino, and cars without liquid cooled turbos.

 

[DoubleWasp]

Some conventionals have pretty high flashpoints, and there's plenty of turbodiesels out there clocking huge numbers on conventional oil.

I choose to run premium synthetics myself.

 

[Pontual]

Originally Posted By: demarpaint
You're right about there. Conventional oil is probably going to start to break down at about 250F or so. Your bearing and turbo temps are probably a lot higher. The transmission temps are a bit high for my liking too.

I'd be using synthetic oil.


Slowly break down, yes, since the peak temperature maybe 280F, 290F is in a flash period of time, not as steady as in the temp measuring point. The oil can handle quick peaks in temperature with minimum oxidation increase, but may use its antioxidant quickier. Now if he shut it down while hot (without a cooling idling), the conventional dino will show its deficiency as compared to a good synthetic oil.

 

[demarpaint]

Originally Posted By: Pontual
Originally Posted By: demarpaint
You're right about there. Conventional oil is probably going to start to break down at about 250F or so. Your bearing and turbo temps are probably a lot higher. The transmission temps are a bit high for my liking too.

I'd be using synthetic oil.


Slowly break down, yes, since the peak temperature maybe 280F, 290F is in a flash period of time, not as steady as in the temp measuring point. The oil can handle quick peaks in temperature with minimum oxidation increase, but may use its antioxidant quickier. Now if he shut it down while hot (without a cooling idling), the conventional dino will show its deficiency as compared to a good synthetic oil.


Yes, which is why I'd use a synthetic oil with the information the OP provided.

 

[CT8]

Are we talking 2016 oils or the 1970's oils?

 

[CarbonSteel]

Originally Posted By: mbacfp
Great question and concern. I have the Cab & Chassis version of the Powerstroke 6.7 (F550 motorhome). One of my nagging aversions to trying conventional 10w-40 vs 5w-40 is driving in those occasional situations. In taking I-15 north to Las Vegas and going up those long grades with the temperatures over 105+...makes me feel better knowing Mobile Delvac 5w-40 is in the crank. However, those environments aren't the norm for me. I have seen those same temp ranges as 2015_PSD.
Heh, I-15 headed into Las Vegas is where I saw some normal temperatures, but I was not hammering it (only 65-70mph). Headed into San Diego on I-8 and in, through, and out of Joshua Tree National Park towards Vegas is where the oil was the hottest. I am thinking I will stick with synthetic oil--especially when towing since the temps will undoubtedly be higher.

 

[CarbonSteel]

Originally Posted By: HemiHawk
Originally Posted By: 2015_PSD
Originally Posted By: HemiHawk
Originally Posted By: Rand
Its more the hottest the oil sees than the bulk oil temp.
Which in a turbo would be a quite a bit higher. Out of curiosity what engine is this?
Not sure if you are asking me or Rand. But if me, it is my 6.7L Ford Powerstroke.


Sorry that was for you sir. I was curious if there was an oil cooler. I know on my turbo car, the oil temp readings never really get too high, but I think its sampling after the cooler. Like Rand mentioned, the bulk temp on that run was high, but the temp in the hot spot (the turbo) will be much higher.

I have always seen that around 250F conventional will begin to break down, which again in a turbo would happen much quicker. On the other hand, I'm sure plenty of turbo cars in the past ran dino, and cars without liquid cooled turbos.
Yes, there are a multitude of coolers, oil and radiator, plus intercooler. I plan to play with the MPH to see what difference it makes.

 

[demarpaint]

Originally Posted By: 2015_PSD
Originally Posted By: mbacfp
Great question and concern. I have the Cab & Chassis version of the Powerstroke 6.7 (F550 motorhome). One of my nagging aversions to trying conventional 10w-40 vs 5w-40 is driving in those occasional situations. In taking I-15 north to Las Vegas and going up those long grades with the temperatures over 105+...makes me feel better knowing Mobile Delvac 5w-40 is in the crank. However, those environments aren't the norm for me. I have seen those same temp ranges as 2015_PSD.
Heh, I-15 headed into Las Vegas is where I saw some normal temperatures, but I was not hammering it (only 65-70mph). Headed into San Diego on I-8 and in, through, and out of Joshua Tree National Park towards Vegas is where the oil was the hottest. I am thinking I will stick with synthetic oil--especially when towing since the temps will undoubtedly be higher.


Smart move using a synthetic going forward. Any idea what the coolant temps were, cruising at those speeds and moving uphill under load?

 

[bullwinkle]

Your F-250 should have synthetic ATF already, should be Mercon SP in the TorqShift. I'm a pretty big fan of Delvac 1 5W40-not sure if it's 249C/480F flashpoint can be beaten!

 

[CarbonSteel]

Originally Posted By: demarpaint
Originally Posted By: 2015_PSD
Originally Posted By: mbacfp
Great question and concern. I have the Cab & Chassis version of the Powerstroke 6.7 (F550 motorhome). One of my nagging aversions to trying conventional 10w-40 vs 5w-40 is driving in those occasional situations. In taking I-15 north to Las Vegas and going up those long grades with the temperatures over 105+...makes me feel better knowing Mobile Delvac 5w-40 is in the crank. However, those environments aren't the norm for me. I have seen those same temp ranges as 2015_PSD.
Heh, I-15 headed into Las Vegas is where I saw some normal temperatures, but I was not hammering it (only 65-70mph). Headed into San Diego on I-8 and in, through, and out of Joshua Tree National Park towards Vegas is where the oil was the hottest. I am thinking I will stick with synthetic oil--especially when towing since the temps will undoubtedly be higher.
Smart move using a synthetic going forward. Any idea what the coolant temps were, cruising at those speeds and moving uphill under load?
The oil temps are digital, but the coolant is analog. It barely moved up from normal on the needle.

 

[CarbonSteel]

Originally Posted By: bullwinkle
Your F-250 should have synthetic ATF already, should be Mercon SP in the TorqShift. I'm a pretty big fan of Delvac 1 5W40-not sure if it's 249C/480F flashpoint can be beaten!
This is my first run of it (have 4 more OCs I my stash), will have to see how it fares, but so far so good.

 

[UncleDave]

This is my normal towing area, and many guys go from LA to the desert rivers and lakes through this route.

Ive seen ambient temps at 125 on these routes.

This is why j2807 tow standard uses the Davis dam grade as one test route, and eisenhower as another, although eisenhower gives you nice cool air towards the top where Mojave/ Davis remains brutally punishing inlet temps the whole time.

Id say sustained temps of 250 and up is where conventional oil starts breaking down.
I like to keep trans temps under 220. Not all that hard to see those temps towing a 7500 LB boat through there, or a motorhome towing a boat.

The brutality of towing through here is why many boat guys are losing their engines altogether around the 100-150K range. Especially chevy and ford 5-6 liter engines.

The mythical Bitog "forever" truck engine that actually sees rated capacity towing is a fantasy in these parts of the US.

UD

 

[mbacfp]

My first run with Delvac 5w-40 as well. Also includes lots of towing with additional 5,000 pound tow car. Will see how it compares to Valvoline Premium Blue 5w-40. Thanks.

 

[Jetronic]

Why guess?

http://www.mdpi.com/2075-4442/3/1/54

Quote:
This work focuses on characterizing the thermo-oxidative degradation of synthetic and semi-synthetic engine oils aged at 120, 149 and 200 °C


Quote:
At the lowest temperature employed, synthetic oil underwent higher rate of oxidation, while semi-synthetic oil was stable for longer time periods. At higher temperatures, the initial rate of change of average apparent activation energy of synthetic oil correlated well with a similar variation in oxidation number. A mixture of long chain linear, branched, and cyclic hydrocarbons were observed when semi-synthetic oil was degraded at higher temperatures.