Ecodiesel towing test. Suspension sag, mpg, power, and cooling

smurfs_of_war said:

Sorry to dredge this up, but one reason nobody has stated not to change the mix in your cooling system is because it also changes the BOILING point, not only the freezing point. More water- easier to boil over. The coolant temp in these trucks handles a lot more than just cool the engine. Keeps the transmission temp in the optimal range, oil, everything. Oil absorbs heat as well, and that is also part of the design- the oil and coolant are designed to keep that engine in the sweet spot for temps. If it's running too hot, you're going to know it. The temps listed wouldn't alarm me at all.

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The difference between the boiling point of a 50/50 solution and a 25/75 solution isn't much. Something along the lines of 10deg F IIRC.

The coolant system keeps the transmission cool, how?

In any event, this is all kind of overcome by events. Once it became clear that the thermostat doesn't fully open until 228deg, any concern re. 222deg went away.

Oil doesn't do much to cool water-cooled engines. If you look at the design of the block and the heads you'll see that most of the combustion chamber is surrounded by the water jacket. This is the design that dumps the heat of combustion into the coolant. The reason the oil gets hot is that it just happens to be running thru little passages in the hot block and head, which is different then being in cavities that surround the combustion regions.

Also, oil is a lousy heat exchange medium. It's around half as effective as water. That's why oil coolers can cool the oil a fair amount, but the cooled oil doesn't cool the engine much. Hmm, how to explain that.....it's as hard to get the heat energy out of the oil as it was to get it in. Years ago I was doing a lot of experiments with the oiling system of my BMW race car. I installed an aftermarket oil cooler 3.5x as big as OEM and put temp sensors before and after. The temp delta was only 4deg between inlet and outlet, which is obviously not a lot. What I didn't expect tho is that the over all temp of the oil was reduced significantly, like 25deg or so, which is a lot. That would seem to be a contradiction but what was happening was that pulling out 4deg in the oil cooler was enough to significantly lower the steady state temp of the system because the oil just wasn't pulling that much heat out of the engine.

RangerGress said:

Oil doesn't do much to cool water-cooled engines.

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The hemis all have oil squirters to cool the underside of the pistons. I'm sure they didn't just put those there for bragging rights.

RangerGress said:

The difference between the boiling point of a 50/50 solution and a 25/75 solution isn't much. Something along the lines of 10deg F IIRC.

The coolant system keeps the transmission cool, how?

In any event, this is all kind of overcome by events. Once it became clear that the thermostat doesn't fully open until 228deg, any concern re. 222deg went away.

Oil doesn't do much to cool water-cooled engines. If you look at the design of the block and the heads you'll see that most of the combustion chamber is surrounded by the water jacket. This is the design that dumps the heat of combustion into the coolant. The reason the oil gets hot is that it just happens to be running thru little passages in the hot block and head, which is different then being in cavities that surround the combustion regions.

Also, oil is a lousy heat exchange medium. It's around half as effective as water. That's why oil coolers can cool the oil a fair amount, but the cooled oil doesn't cool the engine much. Hmm, how to explain that.....it's as hard to get the heat energy out of the oil as it was to get it in. Years ago I was doing a lot of experiments with the oiling system of my BMW race car. I installed an aftermarket oil cooler 3.5x as big as OEM and put temp sensors before and after. The temp delta was only 4deg between inlet and outlet, which is obviously not a lot. What I didn't expect tho is that the over all temp of the oil was reduced significantly, like 25deg or so, which is a lot. That would seem to be a contradiction but what was happening was that pulling out 4deg in the oil cooler was enough to significantly lower the steady state temp of the system because the oil just wasn't pulling that much heat out of the engine.

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Are you serious ?? (bolded statements)


To begin with, he said it keeps the transmission at optimal temp, not that it cools it down.

The cooler in the end of the radiator where the trans fluid connections are serves 2 purposes -
1) it helps heat the trans up to temp in cold weather
2) it cools it and keeps it at temp during normal and hot temps

Remember, the coolant temp you see and were worried about is the temp at the outlet of the block, NOT the temp of the colder water entering, so by the time the water flows thru the block, around the cylinders, then up thru the heads, it has heated back up, and that hot water is what gives you your temp reading. If you have 225 deg at the outlet, with a good functioning radiator, you probably have 190 deg inlet temp. That is where the trans cooler is, the outlet end of the radiator, so the trans is being cooled/heated to that temp. If you have an auxiliary trans cooler, your temps will be even lower. Mine runs well below 180 when towing, and around 150 when not.


Now, for the oil statements- if oil is such a lousy cooling medium, then how is it possible that an oil cooler can easily cool the oil ? If oil is a lousy heat exchange medium, that means it would take a lot of work to cool it. The specific heat capacity (the amount of energy needed to raise the temp of 1 kg of fluid 1 deg) of oil is 1/2 the value of water (2100 vs 4200), so that means oil will heat up and cool down 2x as fast as water. Sorry, it's just science, not personal opinion.

1) Oil is twice as effective at exchanging heat as water is, and that is why it only takes 1/2 as much energy to raise the temp of oil 1 deg as it does water (by exchanging I mean it absorbs and gives off heat much easier)
2) Water is a better coolant because it can abosrb twice as much heat as oil before it changes phase (ie boils)
3) Oil is not meant to cool the engine, only the bearings, which is why it is routed the way it is thru the heads & block..IE small passages with minimal surface area so there is less chance of the oil heating up BEFORE it gets to the bearings and other areas (valvetrain) it is supposed to cool.

The reason it doesn't cool the engine down much is because all the metal in the block is already at the same temp as the coolant, so if all that coolant and all that metal is at a given temp, there is no way 5-6 qts of oil will be able to remove enough heat to significantly drop the metal & coolant temp at all.


And oil does do a good job of cooling, just not as good as water, because unlike you alluded to, it is 2x as easy to heat up as water, but yes, the oil gets hot removing the heat of friction from the bearings and from the forces shearing the oil as it goes thru the bearings. If you didn't have oil to cool and lubricate the bearings, your engine would run a lot hotter than it does, if at all.

If it didn't do a good job, then why is oil the only thing used to cool the big reduction gears and turbines used on navy ships to power them thru the water ?? I mean we can drop oil temp from 120 deg to 80 deg easily using normal temp seawater in only an 8' long cooler handling 1000 gpm of oil ?

TRCM said:

Are you serious ?? (bolded statements)


To begin with, he said it keeps the transmission at optimal temp, not that it cools it down.

The cooler in the end of the radiator where the trans fluid connections are serves 2 purposes -
1) it helps heat the trans up to temp in cold weather
2) it cools it and keeps it at temp during normal and hot temps

Remember, the coolant temp you see and were worried about is the temp at the outlet of the block, NOT the temp of the colder water entering, so by the time the water flows thru the block, around the cylinders, then up thru the heads, it has heated back up, and that hot water is what gives you your temp reading. If you have 225 deg at the outlet, with a good functioning radiator, you probably have 190 deg inlet temp. That is where the trans cooler is, the outlet end of the radiator, so the trans is being cooled/heated to that temp. If you have an auxiliary trans cooler, your temps will be even lower. Mine runs well below 180 when towing, and around 150 when not.


Now, for the oil statements- if oil is such a lousy cooling medium, then how is it possible that an oil cooler can easily cool the oil ? If oil is a lousy heat exchange medium, that means it would take a lot of work to cool it. The specific heat capacity (the amount of energy needed to raise the temp of 1 kg of fluid 1 deg) of oil is 1/2 the value of water (2100 vs 4200), so that means oil will heat up and cool down 2x as fast as water. Sorry, it's just science, not personal opinion.

1) Oil is twice as effective at exchanging heat as water is, and that is why it only takes 1/2 as much energy to raise the temp of oil 1 deg as it does water (by exchanging I mean it absorbs and gives off heat much easier)
2) Water is a better coolant because it can abosrb twice as much heat as oil before it changes phase (ie boils)
3) Oil is not meant to cool the engine, only the bearings, which is why it is routed the way it is thru the heads & block..IE small passages with minimal surface area so there is less chance of the oil heating up BEFORE it gets to the bearings and other areas (valvetrain) it is supposed to cool.

The reason it doesn't cool the engine down much is because all the metal in the block is already at the same temp as the coolant, so if all that coolant and all that metal is at a given temp, there is no way 5-6 qts of oil will be able to remove enough heat to significantly drop the metal & coolant temp at all.


And oil does do a good job of cooling, just not as good as water, because unlike you alluded to, it is 2x as easy to heat up as water, but yes, the oil gets hot removing the heat of friction from the bearings and from the forces shearing the oil as it goes thru the bearings. If you didn't have oil to cool and lubricate the bearings, your engine would run a lot hotter than it does, if at all.

If it didn't do a good job, then why is oil the only thing used to cool the big reduction gears and turbines used on navy ships to power them thru the water ?? I mean we can drop oil temp from 120 deg to 80 deg easily using normal temp seawater in only an 8' long cooler handling 1000 gpm of oil ?

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Hmm. I never got back to this thread. Sorry.

I'm going to try to correct the confusion here w/o behaving poorly. I don't want to do a beat-down particularly because you're just trying to help and I respect that. The problem here is that one of us is a mechanical engineer that positively worked his ass off making it thru years of thermodynamics and heat xfer classes, and one of us is not a mechanical engineer.

1. You have thermal conductivity confused with specific heat. Sure, oil can store more heat energy per degree temp increase because of higher characteristic specific heat, but at issue is thermal conductivity, not specific heat. Thermal conductivity is the RATE at which a material is willing to absorb or dump heat. Specific heat is the amount of heat energy required to raise something's temp. Imagine a 10lb lump of stone and 10lb of AL. Heat them up to the same temp and then sit both on a 12" thick plate of wax. Which will melt thru fastest? The answer is the AL will melt thru faster because it will dump heat to the wax and melt it much faster then the stone will melt the wax it's sitting on. AL has a higher thermal conductivity then the stone so it both absorbs and dumps heat faster. Likewise water has a higher thermal conductivity then oil so absorbs/dumps heat energy more readily than oil.

2. Look up acceptable tranny temps. You'll find that as a general rule trannies like to stay under 200deg. Anything over 220deg is cause for some concern. Since the Ecodiesel thermostat apparently does not fully open until 228deg, the argument that engine coolant cools the tranny fluid has some weaknesses. Sure, engine coolant temp is usually sensed as it comes out of the engine and I agree that a 30deg delta is reasonable for radiator inlet/outlet temps. But that doesn't mean that the tranny fluid is only coming on contact with AL at 198deg F (228-30) unless we know for certain that the tranny fluid is at the bottom of the radiator. Also, just because the engine coolant is at 190deg that doesn't mean that 220deg tranny fluid is going to exit the tranny at 190deg also, that's not how heat exchanger's work.

3. How is it possible that oil coolers easily cool oil. Well that's an odd question to have to answer. Oil goes in one side, there's lots of airflow and surface area to dump heat into, and cooler oil goes out the other side. Oil is kinda hard to cool down, but it's slow to heat up also so it works out. In my experiments with my race car I found 4deg of cooling across the BMW OEM oil cooler and more cooling with large aftermarket oil coolers roughly proportional to the oil cooler's area. Referring to the race car, since the engine doesn't impart much heat energy to the oil, the engine being designed to be cooled by water not oil, dumping 4deg F every circuit thru the oil cooler was enough to cool the entire oil supply down to a much lower equilibrium steady-state temp, call it 50deg if there was no air blast on the oil pan to help cool the oil.

4. Oil is routed thru small oil passages so it won't heat up before it gets to the bearings. No, that's wrong. The bearings are highly dependent on a very reliable source of oil. They are intolerant of even slight interruptions to the oil flow, as are everything that uses hydrodynamic lubrication vs. boundary layer lubrication like cams and rockers. The reason oil is routed to the crank's bearings re. small passages is that it's simply a more reliable design. Run oil thru a big space like the top of a head and it won't be reliably pressurized anymore. Allow the oil flow to go to a number of places before the crank and it would be too easy for a problem anywhere in the oiling system to make the flow to the crank unreliable. So oil usually goes to the cooler, the filter, and then thru the block's oil galley to the crank's bearings.

Your assertion that the reason the oil doesn't cool the block down is that the block and coolant are hot. That's silly. The block is simply designed to be cooled by coolant. The cylinders and combustion chambers are largely enclosed by water jacket. That ensure that the heat of combustion gets to the coolant first. Sure, everything else gets hot too so the it's unavoidable that the oil gets hot. So the crappy little oil cooler bolted on to the Ecodiesel block dumps some of that heat into the coolant and it's the radiator that has to handle the additional heatload. A better design would be a real external oil cooler, but that's something aftermarket types will have to attend to.

With sufficient motivation a person could bolt on some big-ass oil cooler and pull 10deg out of the oil. Lets say that's 1000 BTU/min at whatever the oil flow rate is. That's 1000BTU/min taken out of the engine so it would reduce the cooling load on the radiator. It's not matter of can or cannot cool the block, it's just a matter of working out the numbers.

Re. if oil didn't do a good job why do we use it in the Navy to cool gear trains. That's another odd question. Oil has it's own specific heat and thermal conductivity. It's not good or bad, it just.....is. An engineer makes an assumption re. how much heat energy is going to be generated, then designs a cooling system that will dump, lets say 1.5x that. The design for the heat exchanger takes into account the spec heat and thermal conductivity of both mediums, heat xfer area, and flow rates. You don't even have to use calculus, it's just algebra. Flowing cold water is a darn fine heat sink.

RangerGress said:

I'm going to try to correct the confusion here w/o behaving poorly. I don't want to do a beat-down particularly because you're just trying to help and I respect that. The problem here is that one of us is a mechanical engineer that positively worked his ass off making it thru years of thermodynamics and heat xfer classes, and one of us is not a mechanical engineer.

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Hmmm.........you know nothing about me/my education/ my experience, and it's obvious from some of your replies you are not getting what I am saying because you are too busy trying to prove me wrong. For all you know, I could have a PhD in Mechanical Engineering.

But in passing, I will say this.......when 1000 students graduate from medical school, what do you call the student who has the lowest grades and was last in the class standing ??

Doctor, you still call that student Doctor.

Think about it..........................................

TRCM said:

Hmmm.........you know nothing about me/my education/ my experience, and it's obvious from some of your replies you are not getting what I am saying because you are too busy trying to prove me wrong. For all you know, I could have a PhD in Mechanical Engineering.

But in passing, I will say this.......when 1000 students graduate from medical school, what do you call the student who has the lowest grades and was last in the class standing ??

Doctor, you still call that student Doctor.

Think about it..........................................

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Ok, so the nice approach didn't work. The harder engineering programs, I mean other than ME, all have at least 2 total semesters of Thermo and Heat Xfer. The lighter engineering programs have 1 semester that kinda combines both. Your writing indicates you don't understand heat. You could certainly be an MD and not understand heat, but you can't be a PhD ME and not understand heat. I don't need to know your background to see that you don't understand heat, and that I might help you there. But it would seem that I failed in that. Oh well, worth the try.

I know this is a pretty old thread, but I came across it while researching whether to dilute the antifreeze in my 2017 Ram 1500 Ecodiesel for towing over mountains in the middle of summer.

The stuff RangerGress has been saying is correct, but could cite to some outside facts to address the naysaying. Also, this whole discussion left out a potentially important consideration.

At any rate, diluting the coolant down to, say, 30% antifreeze can* dramatically improve the ability of the cooling system to remove heat from the engine. As was mentioned, this is due to the greater heat capacity of pure water vs antifreeze. What was not mentioned, however, is that more dilute coolant is also less viscous, and so the water pump will actually put more gallons per minute through the radiator than it otherwise would. All the data is here: https://www.engineeringtoolbox.com/ethylene-glycol-d_146.html You can figure out theoretical gains for different concentrations.

Now, note I put a * on the word "can" above. That is because it is necessarily a fact that the engine will cool better with dilute coolant. That's because moving more coolant per minute, and particularly where that coolant is carrying more heat energy, is only going to cool the engine better *if the radiator is capable of removing that extra heat*. This is a big unknown (for me) in this problem... Is the ecodiesel radiator actually capable of ejecting more heat if it's brought more heat? Certainly, the delta between the coolant and the ambient air will be greater, so it will eject somewhat more heat. But how much? I'm just not sure. The fact that the CAC is sitting in front of the radiator is a known problem in terms of cooling these engines... So I suppose driving up the delta between ambient and coolant is probably only a good thing. I'm just not sure by how much.

The other issue mentioned was boiling point. The difference in boiling point between 50% solution and, say, 30% is about 5 degrees. The standard way to address this is to just get a radiator cap with a couple psi more pressure. Of course that means the cooling system as a whole could be pressured by that additional psi. Can everything take the extra pressure? I think probably so but again, I'm just not sure.

The last issue, one that wasn't mentioned, is that diesel engine coolant typically has anti-cavitation additives. I have never been able to determine if the FCA specified coolant has such additives. But if they do, then diluting that coolant means diluting the additives which would be really bad for the engine over time.

At the end of the day, I decided to reduce antifreeze concentration to 25%, bumped cap by 2 psi, and added the appropriate amount of DCA4 additive to address cavitation. That, and changing out the relatively restrictive Big Horn grill for an aftermarket item let me keep the AC running on most hills this last summer.

Running today's vehicles 25-30* hotter is why we have climate change! As to the argument above... I have always read where water cools much better than coolant. Back in my younger days I used to think antifreeze was just that... to keep the cooling system from freezing in the winter. I later learned that it also has lubrication in it for the water pump, gaskets, & engine journals. Is 25% enough to do that? Maybe one of you wise gentleman arguing would know this answer. If so, maybe it would be worth while for me pulling heavy with my gas engine to do this in the summer?