When and how have you personally deviated from the car owners manual

[Brolly]

Mobil 1 Euro 0w-40 in 19 4Runner OR because other countries can go all the way to 15w-40 so I went between.
Mobil 1 Euro 0w-40 08 Honda Accord because it burns oil and I use the 4q left over from the 4Runner fill.

 

[GMBoy]

The funny thing is that in some model years, they published in the owner's manuals that, for 3.6L and 5.7L HEMI engines, in the absence of 5W-20 that meets MS-6935, the owner may use 5W-30 that meets FIAT 9.55535-S1 or FIAT 9.55535-S3. Now, FIAT 9.55535-S1 is your average 5W-30 ACEA C2 oil. Ironically Castrol EDGE and Castrol EDGE EP 5W-30 meet this specification, but Pennzoil Platinum and Ultra Platinum 5W-30 don't. For the sake of the discussion, let's say that any ILSAC 5W-30 will do for a lowly gas engine.

Things get interesting with FIAT 9.55535-S3, which would be an ACEA C3 motor oil. These are mid-SAPS oils with an HTHS of 3.5 or higher. They are emission friendly (SCR, DPF, EGR), primarily used in diesel engines. I believe they chose ACEA C3 to be politically correct for catalytic converters. However, you can run an ACEA A3/B4 oil without ill effects in an MPI gas engine. I prefer ACEA A3/B4 (the precursor to ACEA C3) due to higher starting TBN and because it stands up better to bad gasoline, which is still hit or miss in many parts of the country. German car manufacturers recommended ACEA A3/B4 lubes for their highest performing engines in the US and Canada (MB229.5, for example).

The bottom line is that Chrysler left these little nuggets in their owner manuals over the years, but very few people picked up on them. Until the last few years, almost any manufacturer told owners, more or less covertly to avoid the wrath of the EPA, that a more viscous oil with a higher HTHS should be used if the engine is going to be put to work or abused (towing, track days, etc.).

I plan to write a more detailed post in the future where I go over the VVT, heat issues, lubes, and some other stuff regarding the 5.7 HEMI, hoping that the information will help others.

Bellow is what the Canadian Owner's Manual for the RAM 1500 says (2014 model year):

Engine Oil Viscosity – 3.6L/5.7L Engines (1500
Models Only)
MOPAR SAE 5W-20 engine oil or equivalent Pennzoil®
or Shell Helix® is recommended for all operating temperatures. This engine oil improves low temperature
starting and vehicle fuel economy.
The engine oil filler cap also shows the recommended
engine oil viscosity for your vehicle. For information on
engine oil filler cap location, refer to “Engine Compartment” in “Maintaining Your Vehicle” for further information.
NOTE:SAE 5W-30 engine oil approved to Fiat
9.55535-S1 or Fiat 9.55535-S3 may be used when SAE
5W-20 engine oil meeting MS-6395 is not available

Interesting! I look forward to your post.

 

[Deleted member 89374]

You are being kind, I tend to think of it as a tarted up 5w-30 in drag, masquerading as a 0w-40

My two cents, I believe they missed the mark badly. They wanted an ILSAC class lubricant with an HTHS of ~3.5 for when owners "abuse" their SRT vehicles. These are MPI gasoline engines, so mid-SAPS and absolute fuel efficiency at the cost of anti-wear additives shouldn't be considered a priority. I seriously doubt it saves any fuel, if at all, in its intended application. Yet they managed to force this farce down the throat of many unsuspecting owners who run it just for fear of losing their warranty. Even Pennzoil Platinum Euro 0W-40 would have been a better choice.

I revisited our exchanges about the HEMI, lifter issues, and lubes. Thank you for putting up with the exhausting number of questions and answering them. Putting myself in your shoes would have driven me crazy. I learned a great deal from you.

After that, I started reading old posts by @Clevy. He hasn't been here since 2017. Do you know what happened to him?

 

[Jackson_Slugger]

I have 2006 Holden (Opel) Astra and the owners manual says to use 10W30 or 15W40 in ACEA A3/B3 or A3/B4. That's it. No other viscosity is listed, and no other standards like API are listed.

First oil I ran was Valvoline DuraBlend 10W40 A3/B4 semi-synthetic, close enough. Followed by other name brand A3/B4 10W40s as they are cheap and plentiful here.

I also ran some full synthetic A3/B4 oils such as Castrol Magnatec 5W30, Shell Helix Ultra 5W40, and Valvoline SynPower 0W40. Still no great risk, as they still carried the correct Euro spec, even if a slightly different viscosity grade, mostly the winter rating - which is nothing in my hot climate.

Probably my biggest deviation was Mobil 1 5W30, which was a ILSAC GF-5 and Dexos1 oil, so completely off grade and off spec. But hey, years down the road, and I'm still driving the car.

I had an '08 with the 1.8L. They called for the typical pre-Dexos GM6094 spec here of 5W-30 overall, with full syn or a 0W-30 for extreme cold. The manual specifically said not to use weights like 10W-40 or 20W-50.

I always used a syn 5W-30 or 0W-30, I swear that engine loved "German/Belgium" Castrol Euro 0W-30...

 

[hrv]

First of all... People need to sit down and actually read the book first...

 

[Patman]

I have been deviating from the recommendation for my Corvette since the first oil change. My owner's manual calls for a 5w30 oil meeting dexos1 spec, but I have been running M1 ESP Formula 5w30 which is dexos2. I feel like it's completely safe because in 2019 they switched to recommending a 0w40 dexos2 (with 5w30 dexos1 as a backup choice) And they backdated that recommendation for 2014-2018 Corvettes also. For all intents and purposes, 5w30 ESP Formula is very close in performance to 0w40 ESP Formula. It's operating viscosity is almost identical. In fact, I have always figured I was better off with the 5w30 version because of the larger number of manufacturers specs that it meets.

 

[mattwithcats]

Lets see...
Car is my road car, a 2002 Saturn SL2, Manual...

Tires, original 185/65R15 is "S" speed rating
Current 205/60R15 in "H" speed rating
Inflated to 35 front, 44 rear
5 millimeter wheel spacer in the back

Transmission
Traded the .730 5th gear for a .605. Dropped RPM's by 1000
TES-295 trans fluid

Power Steering filter, coolant filter installed
Coolant changed from Dexcool to Zerex G-05
Motor oil is Mobil 1 ESP 0W-30
Spark plugs are one heat range colder, changed to NGK V-Groove
Pool Noodle in the front grill, for aerodynamics
LED parking, trunk, backup, and dome lights
Longer oil filter,Wix 51516
Installed 6 disc MP3 Stereo from Saturn Ion
Changed PCV valve to fixed orifice no moving part 0.10" hole, PVC1009DL

In progress
Change drum rear brakes to disc
Install fog lights
Oil pressure, temperature gauges

 

[OVERKILL]

My two cents, I believe they missed the mark badly. They wanted an ILSAC class lubricant with an HTHS of ~3.5 for when owners "abuse" their SRT vehicles. These are MPI gasoline engines, so mid-SAPS and absolute fuel efficiency at the cost of anti-wear additives shouldn't be considered a priority. I seriously doubt it saves any fuel, if at all, in its intended application. Yet they managed to force this farce down the throat of many unsuspecting owners who run it just for fear of losing their warranty. Even Pennzoil Platinum Euro 0W-40 would have been a better choice.

Yes, agreed. The SRT cars are already niche, there was no reason to go light on the additive package.

The original SRT 0w-40 was of course just M1 Euro 0w-40. I don't believe the Pennzoil Euro 0w-40 existed at the time, there was just the 5w-40, as I remember sourcing some. Pennzoil was tasked with creating a 0w-40 to replace M1 0w-40 and since M1 0w-40 was likely deemed excessive (with all the Euro certs) the quick and easy way to get that done was to just blend up a 0w-40 and use a conventional SN/GF-5 additive package, since the FCA in-house requirements aren't overly difficult to meet.

I revisited our exchanges about the HEMI, lifter issues, and lubes. Thank you for putting up with the exhausting number of questions and answering them. Putting myself in your shoes would have driven me crazy. I learned a great deal from you.

You are quite welcome, yes, it got a bit onerous near the end but I enjoyed the exchange for the most part. I have no problem with people being inquisitive and a desire for more knowledge, that's what drives me daily in many of the passions I pursue.

After that, I started reading old posts by @Clevy. He hasn't been here since 2017. Do you know what happened to him?

I don't unfortunately. I thought he had maybe been banned (he had a tendency to post things that would potentially rub the mods the wrong way) again and just decided not to come back after the ban was up. I got along with him quite well, so I thought it quite unfortunate when I no longer saw him here.

 

[Deleted member 89374]

M1 0w-40 was likely deemed excessive (with all the Euro certs)

Just my two cents. I think Shell had a "not invented here syndrome" moment. Since they got the FCA contract via the merger, having a different supplier for the high-performance lineup would not look good. Going to an existing 5W-40 would have been perfectly acceptable with an option for cold climates to use 0W-40. I guess, at least back in the day, Shell didn't spend that much on motor oil R&D. Most likely not even close to what ExxonMobil spends. Just my two cents.

the quick and easy way to get that done was to just blend up a 0w-40 and use a conventional SN/GF-5 additive package

You're 100% correct!

the FCA in-house requirements aren't overly difficult to meet

That's very true. However, some of the things they do leave me scratching my head. Like recommend 5W-20, which should be fine, but then running the engine and oil temperatures well above 212F. At least here down south in the summer, 230F oil temperature was the norm, 245F~250F when towing. I know why they do it. However, it's not okay to cause such wear to meet fuel economy standards. I think they do it to further thin out the 5W-20 to a 0W-16 or below. There will indeed be an improvement in MPG, but you should run higher octane gasoline to compensate for the advanced timing. You know about my experiment with the 180F thermostat and no grille shutters. It's running great. I stopped worrying about running 0W-40 in it. I ran RedLine 5W-30 for a little over 3K miles, but it started getting tacky for some reason. At 57F, it felt thick on the dipstick. Then RedLine confirmed via email that they don't do any engine sequence testing on any of their lubes. I got it out, even flushed the engine with LM Pro-Line, and I'm back to M1 FS 0W-40. Since I fixed the exhaust manifold, the engine is silky smooth.

Oh, another funny thing is that MS 6395 lubes aren't even tested on HEMIs as far as I know. Not that it matters anyway.

By the way, I posted in this thread about FCA allowing 5W-30 ACEA C3 lube in the 5.7 HEMI, which I found pretty funny, especially since ACEA C3 is HTHS 3.5 and above.

it got a bit onerous near the end

Trust me, I know. And I also regret my little public rant about Mobil 1, on which I was dead wrong, of course. I got carried away and was concerned with the bad aspect of things. The plan is to beef up the engine in a couple of years, maybe two to three years from now. Install better oil pump (from the 6.2L), Johnson lifters, forged cam, new valve springs, etc. And then mildly tune it. I should do something like that at least once in life. You worked on engines before and had fun, so I am looking forward to it.

I got along with him quite well, so I thought it quite unfortunate when I no longer saw him here.

He seemed to have some exciting posts that I enjoyed reading. Just as I enjoy reading yours, they are pretty delightful, especially in moments when I'm looking to escape or take a break from daily problems.

 

[Deleted member 89374]

@OVERKILL - If I had to guess, I'd say that Mobil 1 FS 0W-40 is your favorite oil right after Ravenol SSL 0W-40. Or at least one of your favorites. I think we are blessed that it's as cheap and available as it is.

Here is a video of a gentleman in Russia trying to find the pour point of Mobil 1 FS 0W-40. I thought it was interesting:

​

 

[OVERKILL]

@OVERKILL - If I had to guess, I'd say that Mobil 1 FS 0W-40 is your favorite oil right after Ravenol SSL 0W-40. Or at least one of your favorites. I think we are blessed that it's as cheap and available as it is.

Here is a video of a gentleman in Russia trying to find the pour point of Mobil 1 FS 0W-40. I thought it was interesting:

​

Yes, saw that in the other thread.

And yes, I have lots of M1 0w-40 in my stash

 

[Deleted member 89374]

And yes, I have lots of M1 0w-40 in my stash

Since I"m running the truck at colder temperatures, I'm trying to decide if I should continue to use 0W-40 in it. I might switch the Mobil 1 FS 0W-40 to use in my 2018 Santa Fe and run Mobil 1 EP 5W-20 in the truck. I also considered AMSOIL SS 5W-20. However, I fail to see how it's better than M1. Here is why I am asking: now that it's colder outside, I rarely see oil creep up to 190F, even after several hours of driving. Now, I don't drive the truck with a heavy foot for the most part, but even when I do, temperatures don't exceed 190F.

I tested again M1 EP 5W-20 at these lower ambient temperatures, and the engine is more responsive while fuel economy is visibly better. I can get up to 20 MPG on winter gas with a light touch on the pedal. With 0W-40, I can't exceed 16 MPG. I might trick it to 18MPG by growing downhill with the foot of the throttle, but as soon as I use power, the MPG is back down again. You may or may have noticed when I updated my signature from RL 5W-30 to M1 EP 5W-20 for a short time. That's when I tested 5W-20.

Here is my question to you:

Based on a post I saw from you, I agree entirely with by the way, I imagine that the PCM knows at 185F~190F that I have a higher viscosity oil in the engine, and therefore, I think it completely disables MDS. We talked about it before, and then I thought it was VVT related, but I remember you assured me it's not. Now, I tried driving with a very light pedal on the highway. The truck doesn't slow down like it would if MDS was on. I tried suddenly accelerating, and the truck is responsive. I can't tell the difference in exhaust notes, though it's hard to know with the stock exhaust. The only thing I see is a dip in fuel economy. So I can only imagine that it disable MDS without throwing a code. IIRC on trucks, the wrong viscosity code is disabled anyway.

Now, had I left the thermostat and grille shutters alone, this wouldn't have been much of a problem. However, as you said, I doubled down on MOFT by running 0W-40 in a cold engine.

So, do you think there is anything to this theory? Because if there is, I'd rather give up 0W-40 than the cold thermostat.

Thank you.

 

[OVERKILL]

Since I"m running the truck at colder temperatures, I'm trying to decide if I should continue to use 0W-40 in it. I might switch the Mobil 1 FS 0W-40 to use in my 2018 Santa Fe and run Mobil 1 EP 5W-20 in the truck. I also considered AMSOIL SS 5W-20. However, I fail to see how it's better than M1. Here is why I am asking: now that it's colder outside, I rarely see oil creep up to 190F, even after several hours of driving. Now, I don't drive the truck with a heavy foot for the most part, but even when I do, temperatures don't exceed 190F.

I tested again M1 EP 5W-20 at these lower ambient temperatures, and the engine is more responsive while fuel economy is visibly better. I can get up to 20 MPG on winter gas with a light touch on the pedal. With 0W-40, I can't exceed 16 MPG. I might trick it to 18MPG by growing downhill with the foot of the throttle, but as soon as I use power, the MPG is back down again. You may or may have noticed when I updated my signature from RL 5W-30 to M1 EP 5W-20 for a short time. That's when I tested 5W-20.

Here is my question to you:

Based on a post I saw from you, I agree entirely with by the way, I imagine that the PCM knows at 185F~190F that I have a higher viscosity oil in the engine, and therefore, I think it completely disables MDS. We talked about it before, and then I thought it was VVT related, but I remember you assured me it's not. Now, I tried driving with a very light pedal on the highway. The truck doesn't slow down like it would if MDS was on. I tried suddenly accelerating, and the truck is responsive. I can't tell the difference in exhaust notes, though it's hard to know with the stock exhaust. The only thing I see is a dip in fuel economy. So I can only imagine that it disable MDS without throwing a code. IIRC on trucks, the wrong viscosity code is disabled anyway.

Now, had I left the thermostat and grille shutters alone, this wouldn't have been much of a problem. However, as you said, I doubled down on MOFT by running 0W-40 in a cold engine.

So, do you think there is anything to this theory? Because if there is, I'd rather give up 0W-40 than the cold thermostat.

Thank you.

It's certainly possible, can you feel when MDS is engaged or not on yours? We can hear it in ours because of the exhaust system, the MDS has a pretty distinct note change.

Yes, the ECM infers viscosity from oil pressure and oil temperature, though MDS should engage even when the oil is cold. Mine was working yesterday and the gauge hadn't even come off the low mark, it seems to start working after a certain amount of time has elapsed, I'd say about 10 minutes. That said, if it notices something funky, it may not enable it and it is certainly possible that this is what you are experiencing.

 

[Deleted member 89374]

It's certainly possible, can you feel when MDS is engaged or not on yours? We can hear it in ours because of the exhaust system, the MDS has a pretty distinct note change.

No, I cannot tell. I could never tell by the sound, ever since I had the truck. When I run 5W-20, and I'm on the freeway, for example, and I step on it all of a sudden, it's like the truck wakes up and pulls like a bat out of hell (very satisfying). WIth 0W-40, under the same circumstances, it pulls good, but it doesn't have that feel of engine responsiveness like it just woke up, if you know what I mean. That's about all I can tell, other than the fuel economy difference between the lubes while running on the same gas from the same gas station. RedLine 5W-30 had even worse fuel economy than 0W-40, though not by much. Cold flow is not one of RedLine's fortes, that's for sure.

Yes, the ECM infers viscosity from oil pressure and oil temperature, though MDS should engage even when the oil is cold. Mine was working yesterday and the gauge hadn't even come off the low mark, it seems to start working after a certain amount of time has elapsed, I'd say about 10 minutes. That said, if it notices something funky, it may not enable it and it is certainly possible that this is what you are experiencing.

Do you know of any tool or software that I can hook up to the OBD II port and read MDS actuation from the PCM? I have AlfaOBD and OBDLinkMX, but I'm not sure if I can do it with AlfaOBD. I haven't found a menu in it where it allows me to do just that. It would be nice to know for sure rather than speculating, as well as share my findings with the forum.

You're running Mobil 1 EP 0W-20, so it takes way less time for your lube to thin out, even in the cold, than it takes Mobil 1 0W-40. Also, I don't have an oil heat exchanger. It's funny that I can even see the holes above the oil filter where it's supposed to be attached. I'm considering installing one within the next couple of months. All of our other vehicles have one and warmup time is much less than for the RAM when it's cold outside.

 

[OVERKILL]

No, I cannot tell. I could never tell by the sound, ever since I had the truck. When I run 5W-20, and I'm on the freeway, for example, and I step on it all of a sudden, it's like the truck wakes up and pulls like a bat out of hell (very satisfying). WIth 0W-40, under the same circumstances, it pulls good, but it doesn't have that feel of engine responsiveness like it just woke up, if you know what I mean. That's about all I can tell, other than the fuel economy difference between the lubes while running on the same gas from the same gas station. RedLine 5W-30 had even worse fuel economy than 0W-40, though not by much. Cold flow is not one of RedLine's fortes, that's for sure.


Do you know of any tool or software that I can hook up to the OBD II port and read MDS actuation from the PCM? I have AlfaOBD and OBDLinkMX, but I'm not sure if I can do it with AlfaOBD. I haven't found a menu in it where it allows me to do just that. It would be nice to know for sure rather than speculating, as well as share my findings with the forum.

You're running Mobil 1 EP 0W-20, so it takes way less time for your lube to thin out, even in the cold, than it takes Mobil 1 0W-40. Also, I don't have an oil heat exchanger. It's funny that I can even see the holes above the oil filter where it's supposed to be attached. I'm considering installing one within the next couple of months. All of our other vehicles have one and warmup time is much less than for the RAM when it's cold outside.

I was actually referring to the Jeep (wife had the truck at work). I can feel the MDS in the Jeep because you sit much closer to the engine.

I have the privilege of having access to a dealer micropod and Witech, so I've not messed around with the aftermarket scanners unfortunately. If it does work, let me know, I'm curious as to what you'll find!

 

[Deleted member 89374]

I was actually referring to the Jeep (wife had the truck at work). I can feel the MDS in the Jeep because you sit much closer to the engine.

I heard that the 6.4 can go on MDS much longer than the 5.7 as it's more powerful.

I'll do my best to find a tool that can tell me when MDS is active. Bellow I used a viscosity temperature calculator to showcase the viscosity difference between 0W-20 that you're running and 0W-40 that I'm running at 185F. Do you think that the PCM can tell a 6 cSt difference?


Mobil 1 EP 0W-20

Mobil 1 FS 0W-40

 

[OVERKILL]

If it bumps oil pressure enough to be "flagged", it's possible.

Consider this: The 0w-20 is 18cSt at 68C (154F).

Yes, the system has some built-in fudge factor to allow for changes in how tight the engine is (wear) and variances between lubricants, but that's a 30 degree F (almost 20C) difference in oil temp to cover that viscosity spread, I'd personally consider that significant, but I didn't write the software, so I don't know how tolerant it is there.

 

[Deleted member 89374]

If it bumps oil pressure enough to be "flagged", it's possible.

Consider this: The 0w-20 is 18cSt at 68C (154F).

Yes, the system has some built-in fudge factor to allow for changes in how tight the engine is (wear) and variances between lubricants, but that's a 30 degree F (almost 20C) difference in oil temp to cover that viscosity spread, I'd personally consider that significant, but I didn't write the software, so I don't know how tolerant it is there.

But that's not even the worse. It says that the cam is "Out of Sync", solenoids #1 and #2 activate when MDS tries to activate but can't when conditions aren't met. Oh, and there is a considerable delay between the desired and actual camshaft position.

I assume that the PCM programming is married to the viscosity curve of 0/5W-20 for the 5.7 HEMI.

I was temped to trigger a CamCrank re-learn, but I don't know if I should do it. The prudent path seems to be to go back to Mobil 1 EP 5-20.

I feel really dumb for listening to "forum gurus" and trying out thicker oils in this engine. After all, my goal is not to mess it up, but rather improve its longevity.

Thank you for your insight. Any thoughts?

PS: The app is called JScan and costs $23.99 per vehicle VIN. It complements AlfaOBD very nicely.

The screenshot was taken in driving with the oil temperature at 183F and coolant at 185F.

 

[OVERKILL]

But that's not even the worse. It says that the cam is "Out of Sync", solenoids #1 and #2 activate when MDS tries to activate but can't when conditions aren't met. Oh, and there is a considerable delay between the desired and actual camshaft position.

I assume that the PCM programming is married to the viscosity curve of 0/5W-20 for the 5.7 HEMI.

I was temped to trigger a CamCrank re-learn, but I don't know if I should do it. The prudent path seems to be to go back to Mobil 1 EP 5-20.

I feel really dumb for listening to "forum gurus" and trying out thicker oils in this engine. After all, my goal is not to mess it up, but rather improve its longevity.

Thank you for your insight. Any thoughts?

PS: The app is called JScan and costs $23.99 per vehicle VIN. It complements AlfaOBD very nicely.

The screenshot was taken in driving with the oil temperature at 183F and coolant at 185F.

View attachment 84187

You are also running the engine cooler than it expects too

The VCT issue may be separate, I wouldn't expect that to have any real reliance on viscosity, but let's see what happens when you go back to the spec visc.

You've modified more than just the oil. You went heavier with the oil, and then also limited how thin it would get by swapping in a cooler thermostat and removing the grille shutters.

I think fitting a factory heat exchanger is a great idea (you said you were considering it). I'd also suggest going back to the factory thermostat at that point, as I know that was the issue you were trying to overcome (oil temp) with the fitment of the cooler t-stat.

 

[Deleted member 89374]

You are also running the engine cooler than it expects too

The VCT issue may be separate, I wouldn't expect that to have any real reliance on viscosity, but let's see what happens when you go back to the spec visc.

You've modified more than just the oil. You went heavier with the oil, and then also limited how thin it would get by swapping in a cooler thermostat and removing the grille shutters.

I think fitting a factory heat exchanger is a great idea (you said you were considering it). I'd also suggest going back to the factory thermostat at that point, as I know that was the issue you were trying to overcome (oil temp) with the fitment of the cooler t-stat.

For me, this all started with trying to compensate for high oil temperatures while towing. Not enough MOFT can cause problems. When I was working on my headlights upgrading them with LEDs, I noticed that they didn't install the grille shutter assembly correctly. The rubber on the side was folded all wrong as someone mashed it in there. I took out the assembly cleaned it up, sprayed silicone on it, removed the shutters in the middle, and put it back. The computer thinks that they're still there. So air is focused on the middle of the radiator now. If Chrysler would have bothered to code the software correctly to open them under certain conditions for better cooling I didn't need to do this. But when you go up a mountain and your oil temp climbs like crazy, along with coolant, and it gets to 245F, then 250F, and so on (some got it as high as 280F), and the shutters are still closed, you start to wonder: "what were they thinking?" So I escalated by going up in viscosity, albeit safely.

Long story short, I triggered re-learning for the cam twice today, It does it with the engine on at 1000 rpm if the temperature is at least 158C. Everything went fine. I have no codes or anything. I didn't have any codes before either. The cam turning delay that I see must be due to the software, and OBD II over Bluetooth isn't exactly lightning fast. I am saying this because I have Zero cam errors. MDS is still disabled, and the "Cam out of sync" status is still showing. And that's exactly how I think the PCM does it.

I think that for the 5.7 HEMI it needs 0/5W-20 mostly for the phaser to change the cam position and engage/disengage MDS faster than on the 6.4L so that it can have an edge on fuel economy. I think that the computer sets that "Cam out of sync" status to disable MDS and slow down the VVT system slightly as a safety precaution to avoid any damage, like engaging/disengaging MDS at the wrong time, with the cam in the wrong position for example. The reasoning behind it is above my pay grade so to speak.

Tomorrow, hopefully, nothing comes up and I have time to change the oil. After that, I will drive it around to bring it up to temperature and read the PCM values again and check if MDS works. If it fixes it, I'll leave the thermostat alone. Honestly, it can figure out the viscosity even with a 180F thermostat. I bet it has preset PSI (or kPa) ranges at certain temperature ranges (some tolerance for wear, differences between lubricant brands/formulations, etc). I'll see what 0/5W-20 I'll find tomorrow that's available, considering shortages and all.