Poll: radiator/trans cooler solution

Don't forget that another important function of the "cooler" is to bring the transmission up to operating temperature quickly by exchanging heat between the engine coolant and the transmission fluid. A separate cooler cannot perform this function.

So you are basically suggesting plugging up the trans fluid fittings on the radiator and simply connecting the hoses to each other?

This has been gone over many times. Some find it acceptable. Not for me. I want the heat exchanger inside the radiator to do its thing: help to get the transmission fluid up to temp to improve economy (thermostat will be open long before transmission is up to full temp)/ reduce start up wear and to provide some transmission cooling particularly in high demand situtations. Do you really think that Honda added this feature just for fun? I don't think they got the engineering part wrong on the need for the exhanger. Its the execution of the design with the corrosion issues where they should have done better.

Why not have improved fittings made with all the original style piping and figure out a way to properly reattach to the heat exchanger inside the radiator? Why not source a quality aftermarket with all brass / aluminum fittings and corrosion proof washers? Why not buy a known quality OEM radiator and simply plan on replacing it every 5 /7 years or so?

Radiators do loose some efficiency over time and replacing will eliminate any concern in this area.

I don't think he is suggesting coupling the hose ends together, but rather connect them to a separate cooler in place of the radiator's 'heat exchanger'.
It makes some sense. The 'cooler' could be bypassed with a thermostat control for those concerned about over-cooling during winter morning starts.

Failure rate is pretty low overall. Replacing your radiator with quality aftermarket or OEM at the 5-7 year mark will pretty much guarantee that you won't have this issue.

Honda thought it was necessary even though it added cost and complexity.

The idea that a cold transmission equals greater wear, poorer shift quality, and lowered power train efficiency seems pretty obvious to me.

I see nothing wrong with it, in principle. At least the way I envisioned it in post #7. I think it would work just fine. Finding a positive way to seal the lower radiator holes would not even be an issue. I would use shop air to blow out and dry the lower tank for the trans then seal it up.
Connect a decent cooler to the hoses. For more mild climates you might not even have to bypass it. The ATF Honda uses from Z1 forward, do not thicken up that much in freezing temps. compared to 'straight ATF (Dexron, etc.). Now if the radiator gets flaky, fix, replace it, etc. keep an eye on the coolant level as well as doing a test of the fluid. But no reason to worry about the trans. outside of normal maintenance.

If you are still under warranty you might reconsider only to keep the 'fine print' idiots off your back should you have an unrelated warranty issue.

Just to be clear here . . .Fluid goes in one side of the in radiator heat exchanger and out the other. If you replace the fittings on the radiator with plugs and take the two hoses that were originally connected to the exchanger and connect them to each other with some sort of union then you will have only removed the heat exchanger from the circuit. YOU WILL HAVE NO IMPACT ON THE FLUID FLOW TO THE EXISTING EXTERNAL COOLER.

Ok, maybe some or most of you haven't changed the Radiator. I have 2 times in 18 months. The first was "the" Honda OEM Radiator failure, the second was a failure of the replacement part due, at least I believe in part to poor shipping/handling by UPS/Amazon & Spectra Radiator packaging. http://www.ridgelineownersclub.com/forums/showpost.php?p=1597706&postcount=56

Now do I believe my CSF Radiator has resolved the issue, possibly, but I'm not taking one apart or "reverse engineering" it to determine if they have "changed" from the corrosion prone "belleville washer"

Now on to the "Bypassing the internal cooler" Since my '06 has no OBD2 output for the transmission temp(that I know of), I cannot monitor temp of my ATF. This being said, the Transmission fluid comes out of the Trans, into a hose, into a hard line on the bottom of the outside lower radiator, into a hose, thru the fitting for the internal cooler, thru the cooler on the lower radiator tank out of the lower tank into a hose, to a hard connection to the trans cooler infront of the radiator to another hose which goes into the transmission. The only part of this which I don't know is the "flow" direction. Maybe someone with a SM has that, I'm unsure.

Sorry if I confused the issue by suggesting the addition of 'another' cooler. It is likely not necessary, and I support simply bypassing the radiator and connecting the hose ends together.

IMO its not worth the effort. I have done aftermarket trans coolers on several cars/trucks but it was because they needed them, either they were high performance cars or trucks that towed a lot and need extra cooling especially in the 90+ temps we have 6 months out of the yr here in FL. In the RL's case the added cooler is not needed so why do it? While yes some do fail so do some aftermarket coolers. The cost of the cooler, new lines and clamps would easily put you at the cost of a new spectra radiator which BTW amazon has right now for $139 and would be a much easier swap.

Also as most stated already getting the fluid up to temp is part of the exchangers purpose. If your in a cold climate your fluid may never get up to temp which can lead to all kinds of problems. Generally if you need a aftermarket cooler in a cold climate you would still run an aftermarket cooler thru the factory exchanger to help raise fluid temp in the cold months. Which in the RL's case this would defeat the purpose of the OP. In a warm climate such as here in FL I have always just ran it direct to the aftermarket cooler and left out the factory exchanger and never had any trouble but were rarely see temps below 30.

If you were to do this I would highly recommend running all new lines from the tranny to new cooler and back. I would not just add a connection to the factory lines and add hose to get it too and from the new cooler. The less connections the better, most failure on aftermarket cooler are either added connections or clamp failure

Pardon me while I step up to my soap box...

The short answer is YES, it’s a design flaw on Honda's part - IMO. I maintain that position based on two realities.

First, the failure mode in question is rooted in well-known, naturally occurring phenomena. Setting aside other (BETTER) aspects of design and implementation, a different choice of material at the mechanical interface of the radiator "could have" resolved this serious – easily avoided galvanic corrosion issue. Perhaps a composite material stable enough to operate in the target environment, or if identical metallurgy in-between and on both sides of the interface were used, this issue would not exist. OEMs are not in the business of building products beyond a limited target reliability range. I would suggest that Honda considered many options - but didn't change direction because anything more than their chosen design wasn’t cost effective and was determined to be… "good enough".

In this case good enough likely meant service life near double the warranty period is plenty good. A certain failure % - both in and out of warranty - are calculated risks to any brand name, so if a "small %" of owners suffer a catastrophic failure during ownership, that's just part of doing business. Since I'm on the receiving end of those BUSINESS decisions, I choose to address them with more seriousness than bean counters do - and seek ways to totally eliminate the possibility of cross contamination of vital fluids - without impacting other serious reliability concerns.

Second, implementation of accepted/conventional designs such as a trans heat exchanger buried inside an engine heat exchanger, doesn’t dismiss the opportunity to innovate. Could Honda accomplish the same thing in a way that avoids a failure allowing coolant and trans fluid to contaminate one another? ABSOLUTELY they could have. Obviously, the "pre-heat" exchanger could have been plumbed in an entirely different way that eliminates all possibility of fluid contamination. I'm positive they considered many alternatives to the final design - I'm equally positive those alternatives were considered cost prohibitive for the overall reliability targets imposed by budget constraints.

In the same way OEMs of internal combustion engines have varying reliability resulting from their implementation decisions - accepted and conventional designs have tons of variables when budgets and target pricing rule the roost. Honda's choice have cost some owners big dollars and inconvenience.

Virtually every product, whether physical or software, has "known bugs" at the time of release to market. Those bugs are addressed and resolved in the aftermarket sector as well as on-going improvements by an OEM - but an OEM has other reasons to invest in those improvements - and almost none of them have to do with improving the user experience - unless of course - there’s risk to the brand name reputation in the marketplace.

Generally speaking, OEM's do a great job of achieving balance in the final product within a price target. As many positive attributes as there are with the RL, this particular short coming is too severe for my personal level of acceptance. "Opinions of others" do have value in the real world and in the context of this issue, there is more than one solution. While it could be argued 3, 5 or 7 year service life with the OEM rad is sufficient, the potential for catastrophe must be calculated by each owner. I'm confident the proposed solution solves the problem – which is 100% elimination of the possibility of fluid contamination and zero impact to engine or trans performance/reliability (in this geographic environment).

As far as “the reported issue being low”, the goal of any proposed solution to an issue is to minimize potential catastrophe. Honda thinks they hit that target when they chose to build the rad/trans cooler as they did, and apparently some forum members agree - but I’d bet real money the folk who took care of their RL’s and saw no signs of trouble yet found themselves on the $h!t end of the stick have a different opinion.

Unknown provenance is the enemy of every used vehicle buyer. Once a new owner of a used RL is aware of this issue - and realizes there is no reliable method to detect a failure that could occur at any time in the future - the only solution becomes preventative maintenance - replacing the rad in a used RL even when it "looks good" and the system operates normally is counter intuitive for some, I imagine. Given the varied experience and quality issues shared by members of this forum, I'm additionally cautious on moving forward with current, off the shelf solutions.

For drivers in this type of climate, I see no downside to this idea. And even in freezing climates, the "damage" caused by flow rates of colder than ideal trans fluid might be less than that of engine lubricant thickened by spending the night at the bottom of a crank case in single digits temps. Obviously, some forum members object to the general idea. Personally, I don’t find fault with questioning certain decisions made by Honda during RL development. Like every OEM, they make a consumer product built for the widest possible range of use scenarios. By definition, that means tradeoffs must be made. This is one of the areas where an OEM tradeoff decision can be remedied without sacrificing reliability in other areas.

But again, that comes from the perspective of almost never having to deal with single digits temperatures.

The 15 year old rad in my 40 year old motor coach gives me confidence with the virtues of an all-aluminum rad. I stuck a scope down its throat about a month ago. She's clean as the day I put her in. <6 Gallons of coolant and distilled water in a closed system works great. BTW: in that application, both engine and trans coolers have pre and post temp sensors and gauges. TMI for some, just right for me as the 100,000 mile 455 Olds/TH425 trans pulls 10,000lbs up long slow grades in the dead of a southern summer. From a service life perspective, an all-aluminum rad would be the last one my RL would ever need - and there is virtually ZERO chance of fluid cross contamination. Problem solved.

As always, to each his own.

Stepping of the box now.

Taking a step back here for a moment.

Oh,

If you want to generate interest a "group buy" for a high quality aftermarket radiator then you probably don't wan't to eliminate the heat exchanger in side. If the company can fabricate a high quality all aluminum radiator with an internal heat exchanger that is built with a reliable fittings and internal / external connections to the heat exhanger then you / they would likely find an eager audience in this forum.

They could also probably build a similar radiator without any exchanger for those who don't want it.

There seems to be some questions as to the feasability of modifying the stock radiator to eliminate the corrosion based failure. I would imagine a that a radiator specialist could disassemble a new OEM radiator and improve the materials and sturdiness of the exhanger fittings and connections. This type of service would also likely find an eager audience.

All speculation aside, if you want to make a convincing argument that the exchanger isn't really needed, you will probably have to do some real work. I would venture to say that the onus is on you to show with hard numbers that exchanger does little, or at least not enough to justify the risks that it might pose. Figure out how to read AT fluid temp, find out what the ideal AT fluid temp is, read the coolant temp, do comparison tests at cold, fully warmed up and extreme conditions etc etc. Till then, Honda engineers, though fallible, have the "cred."

WOW... that went sideways in a hurry ! ! !

So, if I understand correctly, the broadly understood goal is to get us past the uncertainty of what many of us (myself included) consider a poor design (or design flaw if you prefer) with respect to the potentially failing interface between the trans cooler lines & our radiators, Yes?

If I can offer a compromise consideration.....

Instead of trying to recreate a 'better' radiator in it's entirety, how 'bout just fixing the part that's not working properly (the design flaw).
What I would propose is defining a new intermediate fitting that will engage with the radiator, but is made from a material that by design (material selection) will NOT corrode. Make this new piece a simple adapter that can be placed between the existing trans cooler fittings and the radiator, thereby removing the interface that seems subject to corrosive failure.

Anybody else think this might solve the problem???

If so, getting someone to design & fabricate a bunch of adapter fittings would certainly be less expensive than an entire radiator. (not to mention that some of us on here could undoubtedly design the thing)

What say ye to this... or have I just added more fuel to the fire??

My suggestion: just like timing belts, replace the Ridge radiator on a recurring basis, like 100K miles. My 2006 failed at 180K miles.

Seems the cooling coil can fail can occur in 2 ways. If the screw connection nipple pops off on the outside of the radiator then the tranny dumps its oil on the ground, and the radiator empties because the nipple creates the seal with the radiator. New radiator, replace the fluid, back on the street. that was my experience. The horrible failure is when the cooling coil fails inside the radiator, and radiator fluid gets into the tranny.

Well Unfortunately I've read every thread here on the ROC, I found out about this about the same time I was out for Surgery and had nothing to do but lay around and recover for about 3 weeks, I probably averaged 5-6 hrs a day trying to determine what was the best possible method to both Find and Fix this issue. That 's the longest I've ever not worked and the absolute most I've ever read. I've not only read about it here but also on Piloteers, since at the time My dad had a 2005 Honda Pilot and we were both concerned about the issue. I've also read threads on other Nissan, Toyota, and GM forums where this is a problem. At one point I believed this was an "Japanese Design" but I've seen it on Domestic vehicles, although to think about it know, those may have been "Badge Engineered Domestics"

And I do agree with you that they "Must Design it that way" for a reason because almost every OEM has had this issue occur to at least one vehicle or another.

But, unfortunately all my Automotive Engineers have since passed away, or I'd ask them WTF this was all about. But I cannot find in the OM or SM what this is attempting to do. I have yet to determine what direction the flow is for ATF at the Radiator and external cooler. About all I do know it it is one big loop, out of Trans into Radiator into external cooler back to trans or possibly reverse Trans, External cooler, Radiator then Trans.

I'd really like a Moderator or someone with the Honda "Batsignal" or any other automotive engineer to chime in would be greatly appreciated.

As long as we are theorizing about the virtues of "accepted" mechanical designs in the automotive industry, allow me the soap box for a few minutes to offer this theory:

The world of science, medicine, mechanical/electrical engineering (ETC) is full of accepted practices, operational, design and implementation "standards". Some standards are so good, they stand the test of time and are kept in place for decades or centuries. Thank goodness many accepted ways of doing things continue to evolve, otherwise, we'd still be using leaches in medicine and many chronic health issues would still be treated with bloodletting (not to be overly dramatic).

In my wireless telecom life, I deal with outside entities that demand processes based partially in sound engineering and partially in "that's the way we've always done it". I find the biggest challenges and rewards in discovering new ways to accomplish the same goals while simultaneously removing bureaucratic processes that do little more than serve as road blocks to real progress. A recent example of that involved a series of parametric tests in a laboratory environment conducted during device certification. The process is a required multi-level step prior to offering a mobile device to the public for use on a wide area wireless network - it was designed and enforced by a network operator whose name you all would recognize, developed years ago and folded into the ever growing, always evolving tests to certify network interoperability of the mobile phone we hold in our hands today. When the futility of the requirement was brought to light, the ripples that came from its elimination smoothed the way for new products - reducing re-occurring engineering costs for all new OEMs, eliminating calibration of lab equipment that was no longer needed, ETC, ETC, ETC. The only real impact to anyone's job was the lab rat who no longer had to check a box on a process verification form.

The point of that commentary is this: "accepted" implementation of most things is not a static principle. Especially when that acceptance stems from "the way we've always done it". Evolution happens, and the topic of this thread "may be" an area where evolution needs to happen.

I've searched for data on the concept of "pre-heating" trans fluid. Can't seem to find anything on that topic, but that may be due to my own bias when choosing search terms. The Society of Automotive Engineering has tons of white papers, test data and theories on fluid dynamics, thermal this-that-and-the-other-thing, but I'm not seeing data to support the concept of pre-heating trans fluid. In the absence of information to the contrary, I submit this theory:
If the concept of pre-heating trans fluid is to "extend the life of" trans service, I'd suggest it is only being done to reduce the perceived risk of in-warranty failure based on what we on the street might call "urban legend". Indeed, the various implementation methods across many OEMs are causing opposite real world results for some owners. The incremental benefits of the intended goal are the root cause of the death of X% of transmissions that would have otherwise remained in service - and this is happening only to reduce warranty exposure for the OEM. I find it interesting that the world seemed to be just fine before this "standard" was adopted by the industry.

Engineers of any discipline are subject to the same psychological affects "average" citizens experience. For the topic at hand, the "new standard" may have been developed to address an issue experienced by an OEM who implemented a "solution" observed and adopted by other OEMs simply to keep pace with the competition. Hey, it could happen, we've all seen this to one degree or another in our lives.

The point is this: *everyone* understands that transmissions spend the vast majority of their life operating "at temperature". The standard there is keeping the average temp in the very low triple digits is best. Very low triple digits = below 200F (depending on what data set you choose to believe). Average becomes a topic of discussion but lets keep things simple here.

With that in mind, the question becomes: does the passing of "cold" trans fluid - for the short time it exists - improve service life to the level where the risk of fluid cross contamination is offset? I dunno because I don't have quantitative and/or qualitative data to assess an answer either way. And neither do you.

Any OEM is forced to balance production cost and warranty budget accrual against risk, reliability and brand name protection. I suggest the design concept in question here is a broad calculation that minimizes risk in two directions.
1) In-warranty fluid cross contamination potential is low enough for the go-forward implementation OEMs chose. And the (unstated but industry accepted) mechanical benefits of "pre-heating" trans fluid virtually guarantees an acceptable in-warranty mechanical failure ratio unrelated to cross-contamination.
2) The production cost reduction efforts of the chosen design - and the resulting out-of warranty failure rates due to fluid contamination - with the potential class action law suites threatening market place brand name reputation - were based in known ratios/risks acceptable to the OEM.

After all, who expects an OEM to warranty a trans with 100K miles? I certainly don't but I know this: there are tried and true ways to get WAY better life out of vehicle components.

Using Carsmak example, it should be clear to everyone that his results indicate cross contamination happens in a system maintained to expected levels. In his case, the entire (supposed) "benefits" of pre-heating" has the potential to eff his fully functional transmission.

We haven't even touched on the (now) industry accepted standard of plastic upper and lower radiator caps. With a teeny bit of knowledge in the area of castings, molds, injection processes, pelletized plastic beading, ETC, I've never cared for this design. Aside from the many variables in plastic molding processes, the very definition of currently known materials used to cap radiators today is TEMPORARY. The idea for using plastics in rads was born of service life of the assembled radiator, and the GIGANTIC variables introduced by the owners/users/mechanics servicing them. If the majority of owners don't know enough to keep proper fluids in their cooling systems, why should an OEM try to compensate for that behavior by designing rads that "could" last forever if they were properly maintained? The premise is simple: the majority of consumers allow their cooling systems to degrade at a rate that approximates the expected life of plastic components. Because contamination from poor maintenance reduces cooling at a rate consistent with the life of plastic, AND its cheaper to make, the new standard = plastic caps. Case closed - new "standard" adopted by the industry.

Some opinions are based in belief systems such as "OEMs wouldn't do X if it wasn't good". I don't know if this essay above offsets a portion of that kind of thinking but what I've tried to convey is simple:
- OEMs make choices based in financial realities.
- Those realities have little to do with maximum service life of any component.
- Static engineering practices are not a reference standard for the "faith" some folk place in OEM decisions.
- There are better ways to implement certain designs, but financial calculations dictate engineering decisions. "Good enough" is good enough.
- Reliability of components offered by OEMs can be improved upon in the after market.

Stepping off the theory soap box now. Carry on.

Here, Dnick & OhSix, I've opened the spare Spectra (IMHO overall better aftermarket design) and the Honda/Denso. View for yourself.

https://youtu.be/cX7uKDSy_Is

PS, Dnick I believe my earlier assumption of the lower heat exchanger "Falling Away" was entirely wrong, some form of fitting adaption could fix it & isolate it

I didnt read all five pages. Forgive me if I am talking out of my rectum.
My 2000 Explorer was pretty notorious for tranny issues. I added a B&M tranny cooler, a Permacool tranny filter, a temp gauge inside the truck, and a complete flush and refill with Redline tranny fluid.
I said all that to say this, aftermarket coolers and readily available, quite affordable, and pretty easy to instal if you have some basic mechanical knowledge and the ability to fabricate some brackets.
Granted the Explorer did not have the rust / contamination issues the Ridge does. All I did was fun from the cool side of the radiator, to the B&M cooler, from the cooler to the filter, back to the tranny. 170k very hard abusive miles it always shifted like a dream.

Maybe my story helps, maybe it doesnt.

You're spot on with this observation. I stated "stainless" as a tbd presumption. As you said, material selection is critical. Without checking, I would not endorse any material w/o prior validation of suitability. I'm thinking broadly of "corrosion resistant" vs. stainless specifically (although there may be a stainless solution). That needs to include dissimilar metals corrosion of course.

Along those lines... it is only visual, but I could not help but notice in the above video that those threads (aluminum on aluminum?) seem to have developed some corrosion themselves, while the nearby belleville washer seems to be clean as a whistle. I wonder what the two aluminum materials are that are being used here (on the internal threads of the radiator and the external threads of the fitting)?

Head gasket? Please elaborate.

Unfortunately, no (known) automotive engineer (Honda or other) has bothered to mentioned their credentials and comment on the purpose of the in-radiator tranny fluid cooling/heating device design.

Ergo, we appear to be making educated (more or less) guesses as to the exact purpose of the design.

Personally, I would feel more comfy discussing options if we had a knowledgeable Honda engineer pipe in on this discussion and illuminate the collective wisdom gathered here.

But that would be like expecting a Honda engineer to pipe in on the VTM-4 lock/silent failure discussions. I think I have a better chance of winning the lottery.

That being said, the issue is troubling and IMO, should be dealt with by each mfg (in or out of warranty) without cost to the owner, and it should be addressed going forward, if it hasn't already been addressed (on the OEM side).

Ron, do you ever see any issues with your buses radiator/tranny connections failing like the Honda/Nissan/GM/Acura/etc design?

It might be worth me mentioning....
Newer Honda trannys are water cooled. Meaning there are NO cooling pipes whatsoever. Nothing to the radiator at all. ( which makes my job nicer )
There are coolant hoses and a electric pump.
Dont ask me what years or models, I cant say for sure, but I can say for certain I have seen them on Hondas as well as others.
This statement plays into the " needing the radiator for preheating" theory.

For my 2011 Ody, I ordered the transmission cooler that is part of the tow package after frying 3 trannys on earlier Odys. I assume that cooler is standalone.

The transmission fluid heat exchanger in the radiator is not anything new or unique.

In the early sixties I had a '57 ford with AT. It also had transmission fluid piped to the lower radiator tank. This system was identical to the current RL. There must be a valid engineering need for this.

Agree 100% with speedlever on this. *It would be great* if an automotive engineer familiar with the supposed benefits of "pre-heating" ATF were present to remark on the topic. Having said that...

Conceptually speaking, ATF does the job best when its average operating temp is kept below the normal range of engine coolant, so heating one hydraulic substance to match another only to cool it in a secondary process makes little sense - at least from my street level perspective.

SAE research and publications make theories, tests and test results available across a wide range of topics, some dating back to the 20's. Using their web site for queries on this topic, it's not immediately obvious where this concept has been proven to the general level it appears to be accepted in the industry. All I can say to that is WTF?

Mr. DK Millers comments above answer a question I had, which is: "perhaps modern fluid chemistry "requires pre-heating" to support delivery of maximum viscosity characteristics when ATF is cold?" Taking Mr. Millers words as fact, ATF composition from the 50's shatters that question. Also, none, and I do mean ZERO of the many AT equipped vehicles I've owned over the years have not employed a similar pre-heat deign. From that perspective alone (on the surface) pre-heating ATF appears to solve a problem no one knew they had.

Mr. Millers comments also follow the logic of "they wouldn't do it if it wasn't beneficial". This thread has pondered that brand of logic - and until other data comes available, it is my opinion the short term "benefits" of pre-heating trans fluid does not serve the long term interests of owners operating vehicles employing this mechanism. Especially because the implementation chosen by so many OEMs allows for catastrophic failure resulting from fluid contamination - which is what I find so very unacceptable, even irresponsible from a design perspective.

In my commentary in this post and in this growing thread, I see diametrically opposed thoughts/ideas/concepts. Simply put: if pre-heating ATF solves a short term potential wear issue that exposes OEMs to in-warranty failures from "cold ATF", then it follows that pre-heating is good for the long haul.

Questions remain:
Dedicated car guys know stuff. From the nuance of fluid types to wheel bearing grease, to variable 4WD systems, metallurgy and electrolysis. Why do we not know the nuance of the incremental benefits of "warming cold ATF"?

Again, until more information changes things, it is my opinion this "accepted" engineering practice was born of a perceived issue that was "solved" by the OEM who perceived the issue, and that occurred somewhere back in history. The human mind being susceptible to common foibles we don't need to discuss here, the practice of using this "solution" spread and was integrated by many OEMs for reasons more closely aligned with a human malady than an engineering "need". Perhaps even as simple as the school yard justification of "everyone is doing it". Occam's Razor seems to answer this one. For now.

Another factor, I previously mentioned, is the improvement in ATF fluids. They do maintain a better flowing viscosity than previous ones.
Though, not quite scientific, the back porch demo with a quart bottle of standard Dextron ATF and Z1 over a NY winter's night and having the Z1 pour like 20W oil and the base pour like 50W the following morning, is quite impressive if not conclusive to the nth degree. And DW1 should be at least as good if not better.
(I don't know if Joe remembers when he was on the MDX forum some 10+ years ago, and our resident parts guy set up the experiment. )
The rad exchanger idea goes way back to <$1 dollar qt. for premium dino oil. You can draw your own conclusions.