Engine Oil Temp's. for Duramax???

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Joseph Fihn

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Mar 5, 2005
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A friend of mine has a Duramax that is stock but, he has installed a new guage package (from Edge, I believe) that indicates engine oil temps. We live in the Phoenix, AZ. area (1157' elevation) & he just towed his 24' travel trailer (about 6,000lbs.) up to the White Mtns. in eastern AZ. (9200' elevation). That's a 'climb' of over 8000' in about 230 miles. He emailed me that his 'high' recorded engine oil temp was 270*. Most likely, that is not a common temp but, a, short term, spike in temp. I believe he is using Chevron Delo 400, 15X40. He takes VERY good care of his truck, which, is the reason for the guage.

Is a 270* high temp something to worry about? If so, what can be done to eliminate this high temp? Thank you.

Joe F.
 
I wouldn't worry about it at all. Delo is a good oil for high temperatures -- doesn't it have the highest flashpoint out of all the HDEOs?

Regardless, I wouldn't worry taking any HDEO up to "only" 270F.

I assume Fahrenheit, at least. If it's 270 Celsius, well, different story!

Edit: Of course, there will be hot spots where the oil exceeds 270. But still, should be well within what Delo can take. Someone else can perhaps chime in.
 
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I would say the temp is high, wonder where he placed the temp sender? I would not like to see the oil temp rise more than 20 or 30 degrees above the coolant temp in extreme conditions. Can you ask him where he put the temp sending unit?

On another note, engine oil coolers, just like transmission coolers work very well. And diesels do cool down rather fast if you back off the throddle under load, and before you shut it off idle for a few minutes.
 
He mentioned that there was a plugged opening that he was considering using just above where the oil filter is located.

Joe F.
 
I am curious where the Edge is getting it's info from? I realize that the Edge is scanning the data via the OBD port, but I'm not sure where the Dmax takes its oil temps from. As much as I've been around them (and own one) I'm not sure about the eng oil temp sensor. I'm not entirely sure the Dmax even has an eng oil temp sensor, to be honest. Are you indicating he's added one, on the filter mount? There are several ports there; some are "pre cooler" and I think one is "post cooler" IIRC. Most folks don't realize that the Dmax oil cooler is actually right behind the filter mount; they are an intergral component. It bolts right to the block and uses coolant flow down the left (driver) side of the block to cool the oil with a stacked-plate HX.


I'll say this; stock trucks (esp the Dmax) run really well and under control. I flogged my stock Dmax out through the mountains of Co and UT, and the canyons of UT and AZ, and my UOA can back just fine on 10w-30 dino HDEO. Regardless of the temp indicated, if he's stock, the truck and oil are perfectly fine. I added a pyro last year to track my EGT, and realized that was a waste of money. GM has enginered and programmed the truck so that no stock condition can risk the health/longevity of the engine. I suspect the oil cooler is sized appropriately. If the engine coolant temp is good, then so is the oil temp.
 
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I don't remember what year his Duramax is but, it is the one where they seemed to have radiator cooling problems. That may be why he is concerned about engine oil temps. Also, he read on a Duramax website that some folks were concerned about engine oil temps & it made sense, to him. He said that the radiator cooled the TOP of the engine & the oil cooled the BOTTOM.

He tapped-in to the oil filter housing, as I understand, for the sensor. Exactly where, I don't know as I haven't seen the installation. Just the guage. It is a pretty neat guage & I believe it does get a lot of information from the trucks computer.

I have an '03 Dodge/Cummins & when my friend started to develop an interest in oil temps he told me that maybe I should be somewhat concerned, also. I called the local Cummins store & spoke with their shop foreman & he said that oil heating was not an issue with the Cummins engine. I've never heard of this being a problem, either.

Thanks for your comments.

Joe F.
 
The Dmax cooling system uses coolant to cool the entire block, heads, and EGR (applicable to all but 1st gen Dmax). The oil does not cool the bottom of the engine. The oil/coolant heat exchanger has two jobs:
1) warm the oil as quickly as possible to make sure oil is lubricating as well as possible
2) cool the oil to make sure it is not overheated
The goal is to have both the coolant and oil up to operating temp as soon as safely possible, and then have it stabilize. In essence, the oil temps are slave to the function of the coolant temps.


The Dmax with cooling system issues is the LLY second generation variation. The cooling issue is a result of the cooling system not being upsized when they added EGR when moving from 1st gen LB7 to 2nd gen LLY. The first gen LB7 didn't have EGR, so the cooling system was properly sized for that application. This is a point of consternation for many early LLY owners. (Late in the LLY sequence, they updated the cooling system and lead into the 3rd gen LBZ. The very late LLY engines don't have cooling problems. For more info, he'll have to seek out Dmax specific sites; too much to discuss here).

Generally, if his truck was not overheating the coolant, then it wasn't overheating the oil. If he saw 270 deg F on the oil, what were his coolant temps?


Now, I'll also say this about the temps he saw. Generally 270 deg seems hot to us, but it's not all that unique in the lube world for engine oil. Much of it depends upon where the temps are taken. But generally, that temp is not going to coke the oil immediately. It will probably hasten the oxidation of the oil. The only way to know the current condition of the oil is to get a UOA. The FP of oil is way above that 270 temp, so flash fire isn't an issue.
 
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270 F is well on the way to being hot, but is acceptable for a good oil such as Delo. But watch out for high oil consumption and reduced oil life due to oxidation. If the oil temperature got to ~300 F and was held there continuously, that would be the limit of where the engine should be run. In this situation, the engine would be surviving strictly by the grace of the HTHS viscosity.
 
Originally Posted By: Joseph Fihn
He said that the radiator cooled the TOP of the engine & the oil cooled the BOTTOM.

Joe F.


That's a weird statement. Maybe the website was referring to the fact that the pistons are cooled by oil jets, so the pistons will run hotter if the oil is hotter. The Duramax does have conventional water jackets to cool the cylinder bores.
 
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Perhaps the EGR system has a malfunction (certainly not unheard of!)?
I know what I would do: get rid of the EGR.
Is it not true that in some setups (?6.0 Powerstrokes?) the coolant going to the oil cooler is pre=heated by going through the EGR cooler first?

Charlie
 
The Edge units read oil temp in the LLY according to the literature I have, so it must have an oil temp sensor incorporated into the engine. The 2001 GM LB7 manual I have doesn't show an oil temp sender, nor does the Edge manual show it reads oil temp on the LB7.

Most oil temp senders I've seen read sump temp and 270F sump temp seems pretty high to me. If it was measuring the inlet to the oil cooler... which would read higher than the sump or the cooler outlet... I wouldn't be sweating it much.

In the LLY, is the turbo still water cooled as it was in the LB-7? An oil cooled turbo often adds to oil temps.

I'm not an expert on DMax, but if this were my engine, and depending on just where the sender was located, I'd be looking into 270F oil temps.
 
I don't know about the dmax but on the 6.0 powerstroke the coolant goes through the oil cooler then the egr cooler. This is what causes the egr cooler to fail because the oil cooler gets clogged and then starves the egr cooler of coolant. This was due to not getting to sand out of the block when it was manufactured.
 
Originally Posted By: A_Harman
Originally Posted By: Joseph Fihn
He said that the radiator cooled the TOP of the engine & the oil cooled the BOTTOM.

Joe F.


That's a weird statement. Maybe the website was referring to the fact that the pistons are cooled by oil jets, so the pistons will run hotter if the oil is hotter. The Duramax does have conventional water jackets to cool the cylinder bores.


The oil spray on the pistons does pull alot of heat from the pistons to the oil....I would say this is cooling the bottom half to a certain extent.
 
The cooling statement was a repetition of 'old school' thinking.

In many engines more heat is removed by oil than by water.

As pointed out earlier, water/oil heat exchangers both cool AND heat the oil, and it's all good as long as the radiator is large enough to deal with added BTU's.
 
The important thing is time at temperature. If the engine's oil sump was 270°F, then he has a big problem. If the oil coming out of the turbocharger was 270°, then it is probably normal. We don't know where in the lube system he was measuring.

Would he consider a synthetic oil? It will take the heat better.
 
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