Duramax Engine Oil Cooler

[Stlheadake]

I just read an article in MaxxTorque regarding cooling the engine oil. This makes much sense to me. What I read was the first of a two part article, and part one laid out the research for utilizing a separate cooler.

Now in all honesty, I don't normally read this magazine, so I am not really familiar with the author but his research SOUNDS pretty good. His assertion is that engine oil does double duty of lubrication AND cooling, AND that the oil to water cooler is pretty inefficient.

This is only part one which basically explained the problem, and I assume that the second installment will give solutions. The problem is that I can't wait for the second installment.

Anyone have any experience here? Mark do you run a separate oil cooler? John is an extra oil cooler worth it as far as extending engine life, and possibly gaining power (cooler oil=cooler engine temps)?

Is this just hype or is there more to it?

[More Power]

When a question like this arises, I usually ask whether the author is in the business of selling parts that offer a solution... This is one reason why The Diesel Page doesn't sell anything that you can use in or bolt onto your engine/truck.

If there was a persistent need for a "solution" to a problem with the Duramax (like the FSD/PMD 6.5 issue), we'd see the problem show up frequently in the Duramax forum and I'd get at least a few questions/discussions about that problem every month. We/I don't.... I've probably discussed the oil cooling/overheating topic in an email or phone only a couple of times in the past 7 years.

Jim

[Mountainman]

Sounds like "KillerBee" to me! This was a gigantic "can of worms" in another forum where he was eventually kicked off! IIRC, KB was an airline pilot, not an engineer. FWIW, go carefully here cuz there is another solution to the overheating problem that brings down coolant temp AND oil temp that does work! If you don't tow heavy and you don't have OH, why bother. Jim B

[Stlheadake]

I haven't read the entire article yet. This was part one of two..? Basically he was pointing the 'heat' problem at what causes the fan clutch to kick in while towing. His assertion was that this is at least in part caused by excessive heat, and he pointed to engine oil.

Here is the link to the article if you care to have a look: http://www.maxxtorque.com/excerpts/3...oling-part-one

I just finished reading part two, and though he continues to make the case for better oil cooling system, he leaves it at that. Just that the cooling system of the DMax is already fairly challenged (though seemingly sufficient) but by cooling the engine oil directly, the entire engine benefits.

Frankly, I don't really know where I could/would mount an oil cooler. The front clip is at capacity pretty much already. I would think sticking another radiator in front of the other two radiators would only compound the problem.

I was 'fishing' for your thoughts here. I seem to have gotten them. I do tow heavy when I tow, which is only about twice a month on average, and usually only for around a hundred miles each way. Though I live in the mid-west, and summers can be pretty hot, I'm not towing through Death Valley or anything.

Like I said before, I value the info here, and this was another magazine/website related to GM diesels that I found. I don't know much about it other than that.

[JohnC]

Oil to water coolers are not uncommon and for their size very efficient. I don't see how it much matters if you're asking the radiator to shed the heat directly or putting an oil to air cooler in front of the radiator and asking the radiator to make do with hotter air but less heat.

An advantage of the oil to water cooler is much more stable oil temps, albiet sometimes higher temps.

[Stlheadake]

Thanks Jim. I am not going to race out and get one just yet, but I wondered if they had been discussed or what others thought. I suppose you really can't go wrong with 'extra' cooling.

[Hubert]

I liked the articles and sounded pretty good to me. And think it would help the 6.5 as its been reported to have high oil temps. I like your concern on just moving thermo load on the stack no huge benefit in keeping it in the stack but if you add capacity by taking it out to stack then much more cooling.

I agree with John that the radiator/oil cooler helps stabilize the oil temp as the radiator is somewhat kind of sorta thermostatically controlled. Or could heat the oil when coolant starts to circulate. An external oil cooler is not usually really thermostatically controlled.

I'd like to comment more later gotta go.

[More Power]

In the Duramax, the engine oil cooler (stacked plate type) is inline right after the water pump. So, coolant is continuously passing through the oil cooler whenever the engine is running. It's not like a in-rad oil cooler, which sees coolant flow only when the t-stat(s) are open.

The Duramax/Allison equipped trucks do have an in-rad ATF cooler, which resides on the cool side of the radiator, and just upstream from the water pump.

For most Duramax owners, all this is much ado about nothing....

Jim

[Hubert]

Thanks Jim - Uhh I had forgotten a few details. But I think my points should still be valid.

Along the lines JohnC commented on - the coolant cooled oil cooler will still will warm the oil if the coolant is warm and or won't cool it too much if coolant is warm. Where as an external air - oil coolers may not be thermostatically controlled and cooler climate could cool oil too much. I don't remember this point in the articles but its been awhile.

And 2nd point is if the oil cooler is just moved to front of stack then gain is questionable but if sized correctly and placed correctly then cooling capacity is increased.

I agreed in basics of article oil does a fair bit of cooling on modern diesels (ones with piston sprayer's). And oil temperature is fairly important on Diesels under significant load. As oil is what cools the piston (along with intake air). Coolant only cools the head(s) and block it does not cool the piston directly and the piston sees high temps under load.

When I get a chance I'll reread article and try again with clearer post.

With adequate block and head cooling the circulating oil will transfer heat from piston to block and onto coolant. But when coolant is hot and thus the block the oil doesn't shed the heat as well is a different wording.

Normal loads this is not a problem approach more than 85% continous engine load and it is an issue with continuous oil temperature.

[HH]

Since we are on the subject, what is the highest recommend temperature for synthetic oil and dino oil in an engine?

[Stlheadake]

Since we are on the subject, what is the highest recommend temperature for synthetic oil and dino oil in an engine?

I don't know and would be interested, but what I really want to know, is how many out there HAVE a guage for engine oil temp? I never thought of putting one on my liquid cooled engine. I routinely put them on my Dirt Bike (which is also liquid cooled), or air cooled riding mower.

hmmm? Now I have to get another A-pillar cluster and guage....I need a doctor's note, my wife won't argue with a doctor's note...

Calling Dr. Kennedy...

[Hubert]

Don't know about synthetic. Of course they can tolerate higher temps but that doesn't mean its ok for the engine to be hotter see below.

For dino oil the higher the temp the shorter the life expectancy and it varies depending on where you read.

For avg oil pan....
Some like no more than 180~190F which is what I have kind of settled on as its close to coolant temperature and thus is helping cool the engine more. Others say higher is ok. I'll say above 220F is getting hot and shortens life some. The hotter it gets it gets exponential. Say at 260F it should be changed at maybe 1/2 maintenance schedule time.


Of course its engine dependant oil sump size and some other little things but
Kubota says 240F continuous is max and intermittent max is 266F for avg oil temp measured in middle of sump. If above it indicates engine is overloaded. As in probable the piston is really hot from high EGT and heating the oil up.

[HH]

For avg oil pan....
Some like no more than 180~190F which is what I have kind of settled on as its close to coolant temperature and thus is helping cool the engine more. Others say higher is ok.

I know I asked, but I seriously doubt that 180 - 190 would be the limit as the oil is subjected to much higher temperatures being close to the combustion.

After posting, I read the second part of the above mentioned article and he states something like 360 as max temperature. So where is it measured, and anyone have an idea if this is a good number?

I have an engine oil temp gauge and it runs around 220 - 230F unloaded and near 270 - 280F pulling a trailer. I am running 15W-40 synthetic and measuring the temperature right before it goes to the cooler. I am using a tube and fin cooler.

[Hubert]

I am not saying that 180-190F is a hard limit. Yes even dino oil can withstand higher than that. Synthetic cand withstand higher than that. I am suggesting it would be an optimum max continuous temp as to really help cool the engine and take some of the load off the coolant. Also would help keep the piston a bit cooler and help keep it from swelling then gualling under heavy load.

I have never seen a GM spec for max oil temp. And it varies depending on the sources I have read for oil limits.

I have read Kubota's application guide for thier small IDI diesels and they state 248F for continuous and 266F intermittent as limits not to be exceeded. That is measured as "avg" oil temp in middle of oil pan. Its not the only indicator of engine load but it is a hard limit and if you can't keep oil temp below the above specs then they don't approve the application for warranty claims. ie if you run it hot and guall a piston (one the first things that happen for them if run hot) they don't fix it for free.

Now intermittent is rarely clearly defined for these type specs and depends on actual item. Its sometimes stated as duty cycle based on continuos time. Intermittent isn't very long usually and really more a possible high max limit that marketing keys on to show high numbers.

I'd say the oil temps you posted are a bit too high for optimum oil life for dino oil. You are fine because the other key temps limits are in check. Key indicators of load and application EGT, ECT, IAT, oil temp, engine compartment temps. You are generally ok if one is high but its not good for 2 to be out of range if 3 get out of range it leads to trouble 4 would cause damage more than likely (depending on how far over limits).

If you look at maintenance schedules for heavy towing or severe duty they recommend shorter intervals. I think just one of the reasons is due to this higher avg oil temps. Other reasons could be heavy use means more fuel burned and thus more soot and higher temps and more fuel combusted mean other contaminates that dilute additive packages.

[Hubert]

Any one have any other engine company numbers to compare?

I would guess max continuous oil temp would be based mostly on piston cylinder clearance??? As oil Temp., EGT, ECT, and IAT would be the only way to infer upon the piston temperature and thus how tight it gets in the bore when hot and "expanded" or if it is approaching melting or softening temps???

From some heat testing I was envolved with on some Kubota naturally aspirated diesel engines the oil temp tracked right along with ECT and EGT. If either of those were high then oil temp was too. This particular set up had an ECT guage and "murphy switch" and would kill the engine if ECT hit 230F. It appears they size the radiator such that it can't overcool the block as in if EGT and oil temp get high then the coolant will "runaway" as in get too hot and shut the engine off to protect it. Now a quick load up will soar EGT and won't save it. But that's the application technicians job to heat test the application and measure each of the key indicators again EGT, ECT, and oil temperature for normal steady state operation. If all indicators stay within spec then the engine should handle the application. If one is high they should closer examine the loading or reject the application.

I did see some oil temps in 240F range and ECT high but ok. So I don't think its the oil limit its more a combination and inferences.

For the 6.5 GM seems to key on the IAT and ECT together to know the piston may get too hot as that is what triggers defuel. I further suppose they have done some testing and probably its the CHEAPEST (and meets similar repeatability and reliability guage testing) to ensure the OBD system can protect against engine internal damage from hard use (high heat).

[Hubert]

Maybe a good reference:

I googled Deutz (air cooled /oil cooled ) diesel engine. And one reference stated max oil temp was 125C (257F). I guess thats an avg temp and the oil gets hotter at certain points like engine coolant. The air cooled fins max temp is 170C (338F).


http://www.magirusdeutz.co.uk/MD8deutz.htm


Still looking around.

[HH]

Interesting site. Wonder if that temp is specific to the Duetz engines as they are air cooled? Those Duetz engines are pretty cool, (pun intended). Does it make a difference if it is Synthetic or Dino oil? The synthetic oil would help the engine run cooler.

That would be more like a temperature I would expect (275 F). Also where are they measuring the oil temperature? I would expect the max temp for an oil would be specific to that oil, and how long it could sustain that temperature. I am measuring it before it goes into the cooler, as I figure that is worst case, aside from measuring right at the piston. I should install another temp sensor after the cooler.

[Hubert]

Well, at first I thought the air cooled diesel might be a good reference thinking it might be a worst case scenerio but now I am not so sure.

For a normal liquid cooled engine the cylinder walls are cooled via the water jacket and allow the oil to almost immediately start dissipating the heat from the piston into the block and onto the coolant but with air cooled engine the cylinder walls are really hot too and don't really absorb as much heat??? And thus the oil may retain heat longer or absorb a little more heat.

And with an air cooled engine the cylinder walls might get so hot they expands some too where as a water jacketed block doesn't expand the bore as much due to thermal expansion.

I think the synthetics allow better lubrication at the higher temps and help ..BUT IF .. the oil temp spec is some how used to calculate heat dissipation thus knowing the EGT, ECT, IAT, and oil temp they infer the piston temperature then the max oil temp spec should be the same for dino vs synthetic. Just sythetic probably lasts longer at higher sustained temps and may give a slight bump up in intermittent temp but maybe not continuous temperature.

Continuous meaning ....I'll venture is probably anything over 5-10 minutes per hour of operation and could be easily hit pulling heavy and or up a long grade. Intermittent is probably more an acceleration loading.

I am talking about running the engine at or near full throttle & full load for an appreciable time ie a long grade and or towing heavy.

[Hubert]

Also where are they measuring the oil temperature? I would expect the max temp for an oil would be specific to that oil, and how long it could sustain that temperature. I am measuring it before it goes into the cooler, as I figure that is worst case, aside from measuring right at the piston. I should install another temp sensor after the cooler.

We use some big Deutz inline 6 cylinders at work (where I got the idea to look at them for reference) and I looked through the engine owners manual and it says 125C at the oil pan.

I looked on the engine and it has temp probe that appears to be right before the oil cooler. And wired to a warning light and murphy switch not sure when it cuts off at but assume 125C.

The 6.5 pumps from oil pan to filter then to cooler. I figure thats pretty standard route and if you measure right before cooler thats about the same as the oil pan temp.

When Kubota comes to my work to heat test an engine they use a thermocouple that looks like the dipstick. They just measure the dipstick lenght and adjust a grommet to get the same and measure average oil pan oil temperature reading.

[HH]

We use some big Deutz inline 6 cylinders at work (where I got the idea to look at them for reference) and I looked through the engine owners manual and it says 125C at the oil pan.

I looked on the engine and it has temp probe that appears to be right before the oil cooler. And wired to a warning light and murphy switch not sure when it cuts off at but assume 125C.

The 6.5 pumps from oil pan to filter then to cooler. I figure thats pretty standard route and if you measure right before cooler thats about the same as the oil pan temp.

When Kubota comes to my work to heat test an engine they use a thermocouple that looks like the dipstick. They just measure the dipstick lenght and adjust a grommet to get the same and measure average oil pan oil temperature reading.

Good information thanks for looking into the question, I wish there had been more discussion.