Duramax Engine Oil Cooler

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?

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

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

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.

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.

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.

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.

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

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.

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

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Originally Posted by HH

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

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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...

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.

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Originally Posted by Hubert

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.

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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.

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.

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).

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.

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.

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.

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Originally Posted by HH

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.

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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.

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Originally Posted by Hubert

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.

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

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Originally Posted by Hubert

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.

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Measured something today that was not what I expected.

So I am doing some more heat testing on a 4 cylinder IDI TD 87hp Kubota engine. Its a stationary piece of equipment. Today was too cool to really test for overall cooling capability but I can't wait on the weather and had to test some other functions so for information I measured top and bottom radiator hose and avg oil pan oil temperature. Procedure is to block thermostat open about 1/4 open so it can't shut but it can open farther then run and measure temps.

Top hose 147F, bottom radiator hose 134F, oil temperature 241F did not get EGT ambient was 46F. The oil temp was a surprise to see it so high in relation to ECT. And leads me to question if oil dissipates much heat into the block and then into coolant. Engine load varied probably from about 30 hp load to 60 hp with random cycling between the two loads and some time inbetween. The engine is set at fixed throttle position and load varies. Old mechanical injection type as in not common rail or electronic in any way.

Earlier in the week I was seeing 187F top hose 174 bottom hose and 246-255+ oil temps with 850 ish EGT before turbo with a much steadier load.

This engine does have a small coolant to oil heat exchanger and with lower hose at 134F I would have thought it would cool the oil pretty good. So I am not so sure what to think right now.

MAYBE the cool ECT kept the cylinder walls cool and minimized thermal expansion. The load was randomly cylical (pretty quick load and unload) which may have caused spikes in EGT and thus piston temps such that friction from hot piston and cool cylinder caused more heat for the oil ?????

Not sure I have said this but in general I thought the oil dissipated heat into the block as it was pumped around and drained back to oil pan as long as block was cooler than oil. And coolant carries heat of block away if coolant was cooler than block.

But coolant was pretty cool ( lower than std operating temp) but oil temp was high so now I question just how much heat oil dissipates into the block.

One Kubota tech said well.... Oil temp is slow to react in either direction much slower than coolant temp. And further implied I may have measured a low coolant temp momentarily and oil temp was lagging behind. Probably but dang that's awfully big difference especially as cool as it was and don/t think there was much load on engine and when there was a load it was quick.

Chirp Chirp Chirp (cricket sound)

Hey its not a truck but relates as it is similar and reflects some info on the subject.

Today ran another heat test. We remote mounted the oil filter and a cooler. We plumbed in some Tee's and ball valves. We ran with a remote mount oil filter in one mode and with an additional fan powered direct air cooled oil cooler plus the remote mount filter in other mode. We also added a much more aggressive fan on radiator and increased air flow around engine and through radiator. We were able to drop top and bottom radiator hose temps by approx 10-12 +/- degrees to ~176 top and ~156 bottom but still had near 252 oil temp with max loading with oil not circulating through external oil cooler but through remote mount oil filter. Ambient was 65 ish. This was some improvement in oil temps vs some other testing. Appears a decent amount of heat radiates out of oil filter "can" when its remote mounted away from engine/componet heat sources. And air flow over engine specifically the oil pan, filter, and valve cover helps reduce oil temps. Then we switched ball valve to send oil through cooler. Oil temp dropped to 232 ish a ~ 20 degree drop. And soon saw a 5-7 degree drop in coolant temp at top hose with same loading just due to added oil cooling.

So depending I think adding additional oil cooling can reduce load on coolant at least somewhat (at least when engine has a coolant to oil cooler).

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Originally Posted by Hubert

Chirp Chirp Chirp (cricket sound)......

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Give yourself a little more credit. Keep it coming. Very interesting and informative.

Thanks by the way Dmax.

Nothing new to report right now but wanted to make a correction....

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Originally Posted by Hubert

The 6.5 pumps from oil pan to filter then to cooler.

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The 6.5 normally pumps from oil pan to cooler then to filter then to oil gallery. I mixed that up from memory.

Note the Kubota I was referencing has the oil to coolant cooler attached as part of the filter base such that it appears to also pump from pan to cooler then filter.

Wonder if thats so oil won't be too hot and thin and too easy to squeeze more crud through the filter??????

Either OR filter or cooler first if you measure at input to cooler it should be close to oil pan more than likely and a decent avg oil temp reading.

The filter can only remove particulates, so the oil's being thinner has little effect, other than to allow it to pass through more easily.

Thats sounds right but you never know what really happens unless you test it and know. Maybe others have? My first thought would be hot and thin through the filter would help reduce pressure drop across media and be a good thing. Also filtering first would also be desired to reduce circulating crud to the cooler. So I was a little surprised to see cooler first in route. Probably just easier "plumbing". Just something I questioned and said hmmm. Does it matter either way - doubt it.

Engine oil filters generally are not absolute and rely on multi pass filtration was kind of why I thought maybe too thin and it doesn't "scrub" through the media enough. Just a thought.

A very interesting thread and a subject that I have spent many hours on in research as well as in application on my truck. I have yet to find a posting from anyone who has installed a engine oil temperature gauge on a Duramax; so base line numbers on temperature range are not there for comparison as far as I know. This, especially to me, is unfortunate as I cannot really evaluate my own results after installing an oil cooler on my truck. And yes, shame on me for not installing a guage and doing testing before hand, but that is sadly the case, guilty as charged.
My install was a Setrab 920 cooler mounted about a foot and a half forward of the fuel cooler and plumbed with high temp. 'blue' 5/8" hose to 10AN fittings in a Earls adapter with passages slightly opened up for full 5/8" passage. The Earls adapter features a 175 degree thermostat. The cooler originally had twin fans but I found that there is enough air flow in the cooler location that the fans and shroud when not turned on are an air restriction and with them removed the cooler works as well if not better. A caviot to that is that of course when stopped or at low speed the fans should be better, but I see no need for the additional flow under those conditions. A digital oil temperature gauge was installed with the sensor installed in the oil pan drain plug after drilling and tapping to 1/8" NPT.
I find as stated earlier that the engine oil temperature is very slow in rising to a level that matches the overall heat load but it seems to lower noticeably quicker once an excessive load is removed. It takes a good bit of driving time to get the temperature up to 185-190degrees. With winter temps you rarely exceed 165-175 around town. Cruising speed in the 95degree ambient range will keep the oil at 195 to 200 degrees. The extreme that I have seen, and I really don't think I could get it much higher, is 241 degrees while pulling a 16,000lb fifth wheel up La Veta pass in Colo.. This is about a ten mile severe grade, with a strong cross headwind and the temperature I'm guessing in the 85 degree range. I pushed pretty hard mainly trying to keep the EGT's below 1400 degrees and topped at around 60MPH. After topping the temperature fell pretty rapidly and I would estimate was back to normal within 3 miles or so.
The fan clutch very rarely engages anymore, but that is due in part to the fact that I have also added another 920 as an auxilary radiator and a MikeL transmission cooler. If I could ever figure out how to control the EGT's the truck would be virtually unslowable. All additional cooling seems to work in harmony and assist in keeping the overall heat load in check even under the most severe and demanding conditions, except that they really seem to have very little effect on EGT which is somewhat surprising to me.

Randy

Surely somebody out there has a Duramax with an oil temperature guage who can supply some baseline temperature info???

Randy

The stock oil cooler is in the water jacket, so the oil temps should track the water temps pretty closely.

That is definately not what I am seeing, but of course that is with the additional cooler. I am cooler on the unloaded end and higher heavy load. I would thing without the additional cooling both ends would be substantially hotter.....to what extent I would really like to know.
Randy

This is an interesting thread. From my time as a marine engineer I remember that a diesel engine can expose oil to a temperature of 600f at the top compression ring. I would be interested to see what the oil temps in our engines are under a variety of conditions. As this is directly related to engine temperature which is also related to coolant temperature one can assume that oil and coolant temperature have a direct relationship although not proportional. For this reason I always assumed that coolant temperature was monitored as the best way to to recognize an engine that is overheating. Am I wrong?

As oil absorbs and releases heat at a slower rate than water I would expect that oil temperature exceeds coolant temperature by a good margin except, perhaps, for that initial warm-up period. My coolant, once the engine is warmed up, runs at 100c according to the DIC. This is the point at which both thermostats are open. (See this explanation http://www.votechusa.com/DuramaxThermostatOperation.pdf). I would have guessed that the oil temperture would be therefore in the 110-120c range.

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Originally Posted by 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

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Yes that is Killerbee. Killerbee is a quite a nice guy in person, and knows how to work a slide rule quite well. He's a quiet, well meaning guy, but tends to get caught with his pants down due to a lack of practical knowledge of how things REALLY work. This can make him dangerous. Also, his test methods are quite often called to question. The most notorious was when he started tuning with EFI Live and posted that he was getting 28.5-30.5 mpg. I can see the average Joe being fooled by the errant DIC calculator after buying an off the shelf tuner, but when a guy is a self proclaimed expert and engineer, he needs to know the basics and VERIFY the results before preaching to the world. Any supposed man of science should have known to check miles driven vs. gallons used.

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Originally Posted by 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?

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Scott (off topic)

Some time back you asked if there were any updates to the tune you were running. Yes there is an update so if you'd like to email me we can make arrangements.

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Originally Posted by 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.

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Quite some time ago we did some dyno work here regarding overheating LLY's when towing. This is where KB got his idea for engine oil cooling. Rick Lance brought an add on cooler and hoses to test. We did find that oil temps do get very hot and there is a definite benefit to removing heat from the oil. What we ended up doing to exaggerate the cooling was to run the cooler in a pail of water as we could not get REAL world cooling air (My 10HP 36" fan does a good job, just not 60mph worth) on a stationary dyno. We did find that reducing oil temps helped with coolant temps as one would expect.



Additional oil cooling is definitely a good idea for those who tow. Necessary? Maybe not, but just be sure of one thing: Make sure that you use VERY high quality components, route them safely, and inspect routinely. Taking your engine oil out through a system of hoses can produce catastrophic results if there is a component failure. I'm sure this is part or why we have an internal oil cooler on the Dmax.

Another small diesel engine for reference.

Talking to another engine application engineer. This time Yanmar Diesel.

They use an oil limit of 120C = 248F measured in an oil gallery as oil temperature limit. I think its measured between the pump and cooler.

They also appear to pump from sump to coolant heat exchanger cooler then to filter. But I have only glanced at the engine and haven't had the opportunity to application test one yet. If I do I will post anything interesting.

I haven't really studied the flow path or anything, but my Yanmar (Deere 3720 turbocharged AND intercooled) has what appears to be some sort of external coolant type plate exchanger at the oil filter base. Pretty simple design.

The Yanmar and a couple Kubota's I have seen do this too. I think the oil flows to outer side of filter then clean oil back through filter knipple. So I am assuming a bit because when you take the oil filter off the base you can see a little bit of the cooler through the outer side filter inlet So I interpretted is as the oil was being cooled on its way to the filter. But since its proximity and reading Kennedy's reply I better go back and say I guess it has to get cooled some in both directions at the base of the filter. But Looks like more surface contact on inlet side of filter. I don't know either might be some kind of double pass cooler???

They are both pretty small coolers by the way. The small 25 hp Kubota did not have a cooler but the 30 ish hp Yanmar does have a cooler. iirc the Kubota's start with coolers on the 49 hp and up that I have seen.

So been doing some testing with Yanmar this past week.

Just some related info.

Reaction time ?
Starting a cold engine then loading to steady load it takes the coolant temp 20-25 minutes to plateau - stabilize. Oil takes 45-50 minutes to stabilize.
They correct sump oil temps (dipstick thermocouple) by adding 8 degrees to be the same as the oil gallery temperature. I think we are loaded to about 80% so this could be different depending on load.
Not sure how fast the reaction time is starting from a warmed load cycled engine is. The long reaction time for oil is probably due to the heat coeffecient of oil but also too to me shows the significant temperature gradient and different flow rates for the oil depending on location to heat source(s) and cooling.


Kubota shuts thier engines down at 230F ECT. Yanmar is 221F. Measured right before the water neck thermostat. Same max oil temps at 248F.

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Originally Posted by Hubert

Starting a cold engine then loading to steady load it takes the coolant temp 20-25 minutes to plateau - stabilize. Oil takes 45-50 minutes to stabilize.
They correct sump oil t

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On reread that sounded fishy. But its with the thermostat partially blocked open (part of the factory heat balance test procedure). It takes that long for the radiator to heat soak and peak out at its heat load balance.

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Originally Posted by Kennedy

Additional oil cooling is definitely a good idea for those who tow. Necessary? Maybe not...

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The Duramax has been on the road now for coming up on 9 years. Except for the few LLY trucks, overheating is something that most don't need to worry about. And, lubrication failures are even more rare.

There was a 2-part article series in Diesel World magazine a few months back that discussed cooling system upgrades for the LLY. Basically, they simply installed the larger LBZ engine-driven fan and matching fan shroud. ;)

Jim