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0w30 better than 0w20?

8K views 29 replies 11 participants last post by  57chevythunder 
#1 ·
Okay everybody that is my question of the moment: Wouldn't 0W30 oil actually be a better choice than 0W20 for use in our GM vehicles with the 1.5T ? -and by better choice, I mean as far as "long term wear protection" goes.

For the past several months I have spent hours and hours reading every article I can find on the 0Wxx motor oils. I think I am understanding the basics, and will be glad to share what I have found. But I certainly would like to "brain storm" with others on the topic.

Yes I know I know,,, "just use what it says in the owner's manual" and forget it." Well, I am one of those pesky guys that "over-thinks" the topic. I am also that guy that is quite content to care for, service, and maintain all of my vehicles as if they will always be like new, and last forever. (quite frankly, I invite anyone to inspect any of my "fleet" for over-all condition. -especially mechanical.) -that includes the 2019 Eqinox, 2015 Impala, 2002 GMC 4x4, and a self-built 1957 Custom Flatbed Chevy street rod truck.. (now you REALLY know my questionable level of sanity,,,,)

Thanks !!
 
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#2 ·
Okay everybody that is my question of the moment: Wouldn't 0W30 oil actually be a better choice than 0W20 for use in our GM vehicles with the 1.5T ? -and by better choice, I mean as far as "long term wear protection" goes.
I think the answer to that is what part of the country you live in.
I live in Tucson where the average temps are 60F to 110 F.
5W30 works for me, ask bobistheoilguy.com
 
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#3 ·
Excellent point. -and I see you have the "LFX" engine, which is what we have in our '15 Impala. (my gosh, I bet that LFX is very impressive in the 'nox.!!) We totally LOVE our impala, and it gets a pretty consistent 30+ mpg on the open road. I think 30mpg will be pretty iffy on our little 1.5T, but time will tell. -so far it has been used almost entirely short-tripping around town, and giving us around 28mpg, which is GREAT.

Anyway, 5w30 is what the LFX specs, and is no doubt absolutely the perfect choice.
However, the 2018,19, etc. 1.5T "LYX" specs 0W20. -which prompts my question, why wouldn't 0W30 be even better. We would still have the low viscosity for cold starts, but then have 30 weight protection at normal operating temps (around 200 F.)

I found this little tidbit very interesting: The same 1.5T engine as used in the 2017 Malibu specified using 5w30 oil. Which prompted me to research various engine parts for both the '19 Nox, and the '17 Malibu. Well, low and behold, every OEM part I checked was exactly the same for both. -and that included crankshaft assy, crank and rod bearings, camshafts, VVT cam phasers, and the oil pump itself.

BTW, I am registered over at BITOG dot com, and not meaning to show any undue disrespect for that site, the truth is I find it extremely challenging to extract actual facts from all of the rampant opinions. On the other hand, "Tech Facts not Myths" (540 RAT - Tech Facts, NOT Myths) seems to really focus on proven test data. And as I spent gobs of hours reading through those hundreds of pages, it is very apparent that he drives home the point that in most engines a 30 weight oil affords the best protection at normal engine operating temperatures. (and it goes without saying that a 5W or even 0W is best for "cold starts.")

Thanks rednox301
Anxious for other members thoughts too !! Keep them coming !!
 
#5 ·
Hot climates then no zero oils for me. Had several Sables that spec'ed 0-20w. but always used 5-30 in them as prior years with same motor spec'ed 5-30 . Thin oils are for extracting minute mpg's. for EPA ratings not for engines to last 200k miles that is my goal.
 
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#6 ·
Thank you repairman54. And from all of the material I've poured through, your last sentence makes 100% perfect sense.

-and when we think about the actual factual real-life oil temperatures that our engines operate with, we discover that it is always in a range of from lower to mid 250 degrees F. (apart from the warm-up, of course). And that is pretty much independent of what part of the country we live in. -the perfect argument for 30 weight.

I'm even more convinced that the 30 weight rating at 212 degrees makes the most sense. And since both of my cars are kept in our heated garage all winter, even the 5W cold rating should be fine I suppose.

And assuming faithful oil changes, I'll bet that you will EASILY get 200k miles from each of your vehicles.

Is your '20 Traverse getting good gas mileage?
 
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#12 ·
-and when we think about the actual factual real-life oil temperatures that our engines operate with, we discover that it is always in a range of from lower to mid 250 degrees F. (apart from the warm-up, of course). And that is pretty much independent of what part of the country we live in. -the perfect argument for 30 wei
Just one last thought, 95% of the time the engine will run at 195 to 250 degrees, but at start up to the 250 degree mark, most of the engine damage will be done.
Cheers.
 
#11 ·
Very interesting information !! "Keep them coming" !!

I've also noticed that GM has monkeyed-around with their recommended oil filter numbers on several engine/vehicle applications. Crazy,,, It think on numerous ACDelco oil filters, the "R" suffix designated the higher burst pressure rating. And the "e" was for the "E-Core" nylon center core, vs the perforated metal. (possibly to enable higher flow rate through the media?) And there was a GM Tech Link article that explained the change to a 22psi bypass valve. I think that is probably to prevent the bypass valve opening if not absolutely necessary, thus reducing the likelihood of "trash" that the filter has trapped (lying on the bottom of the filter can) getting flushed out and into the galleries.
All the more reason to use "the right??" (whatever that is) high quality filter with the 22psi bypass. (another topic I have researched like crazy,,, and have narrowed my personal choices down to a few,,,)

And the idea of sticking with the OEM recommended oil throughout the warranty period is certainly "safe" as far as potential engine failures resulting in a warranty claim. (-even though many of us have good reason to believe there are better choices to be made as far as the greatest level of wear protection and greater longevity goes,,,,)

Also good thoughts about whether or not there is any operational factor with the VVT system as related to the 0W20 oil spec. I do have definite thoughts about that, but I will make a separate reply, rather than making this one too long.

Thanks again to everyone for the great material !!
At this point, I'll have to say that I am totally impressed with this TerrainForum !!
You all appear to be "GREAT Thinkers !!! -and polite, -and logical, and,,,, okay, I'll stop.
But I think you know what I mean, because some forums are so full of defensive biases,,,,
 
#15 ·
I would still just stick with the recommended 0W20 as I thought this change was done originally to prevent the potential for low speed detonation which was caught on the Malibu 1.5L (maybe I am recalling that incorrectly). I'm not sure what the differences are between the Malibu 1.5L and the Equinox 1.5L but they carry different engine codes and have different power levels. Either way, it is probably more important to keep whatever oil that is in it clean and not go by the OLM.
 
#19 ·
Good input. Thank you. And you are so right on about keeping it clean !! -on that note, I'll share a tidbit from our local Chevy dealer. Well before I decided to buy our 2015 Impala (the only brand new vehicle we've ever had) I was visiting with the service department, asking many questions, and seeking any valuable advice I might get from their experience. I'll never forget what they said: "Harry, the very best advice we have for you is simply this: Watch your OLM, and when it gets near 50% get it in here for oil change service. NEVER EVER run it down anywhere near zero."
As it turns out, they were speaking from experience of having several 3.6 engines that failed, due to worn out cam drive chain sets. -all from customers who "trusted" the OLM.

Yes I've read about the issue with low speed detonation. And I believe that was what drove the additional "Gen 2" requirement on the the motor oil. We must now be certain to only use oil with the "Dexos 1, Gen 2".specification.

Thanks for your input !!
 
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#16 ·
Full synth. Dexos approved oil and a quality filter is all you need. Took my '09 2.4 Malibu to 190k miles and a '99 Yukon both to that mileage and sold them running fine on SuperTech full synth. 5-30w oil and usually Wix filters. ST oil is Dexos gen 2 approved also meeting current vehicle specs. and cheap to buy.
Traverse is same or better than my 'nox on gas as it has FWD mode vs the 'nox being AWD.
 
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#20 ·
Thank you Sir. Great advice. (funny about the Wix filters: In my garage you will see a case of them for each of our different vehicles,,,,) Granted, there are probably a few others out there of even better quality, better micron ratings, etc., but for an industry-standard reliable high quality filter, we are on the same page. -I even like the Napa "Platinum" line- (same as Wix "XP" I think,,,)

And I totally LOVE all of the high mileage reports !! (I had an old 1990 Chevy 1/2 4x4 that was just short of 250k miles when I sold it. -also running perfectly, no oil consumption, etc. Would probably still have that one, but my "truck" needs changed, and I found this 2002 GMC, which has been 100% reliable too.)

Thanks for your input !!
 
#18 ·
I have the 1.4L T in my Sonic and the owners manual calls for 5W30. But then the 1.4L didn't have the detonation issue and is not direct injected.
 
#22 ·
I think this is how I did it.
Sign in and go to the three dots in the upper right hand corner.
Click on three dots and then on FAQ.
When the FAQ menu drops down go to create a signature, click on it, and follow the directions.
 
#25 ·
copied this off of a Vette forum, interesting read
_
High-Temperature/High-Shear (ASTM D-4683)

This test is a simulation of the shearing effects that would occur within an engine. In fact, it's actually designed to simulate motor oil viscosity in operating crankshaft bearings. The D-4683 is measured by the Tapered Bearing Simulator and simulates motor oil stress at temperature extremes.

You might recall that multi-viscosity petroleum oils tend to use long chain polymers to "beef" themselves up. Under high stress conditions where shearing can occur, these polymers break down.

As they do, the viscosity of the oil decreases. This is what the High Temperature/High Shear test checks for.

The HT/HS test is measured in Centipoise (cP) as the Cold Crank Simulator test is. However, in this case, because you're hoping for the least loss of viscosity with an increase in heat and stress, you want the cP value to remain high (at least relative to the minimum set by the SAE J300 standards).

Each SAE multi-viscosity grade has a specific lower limit for the HT/HS cP value. If a multi-viscosity oil cannot achieve a cP value above that limit, it cannot be classified under that viscosity grade. For instance, according to the SAE J300 specifications, an oil must achieve an HT/HS cP value of 3.7 or higher in order to be classified at the 15w40 viscosity grade.

So, whether this data appears on a manufacturer's tech spec sheets or not, the company has the data.

They have to in order to classify an oil as a certain multi-viscosity grade. Of course, this does not apply to monograde oils although some companies run this test on those oils as well.

WHAT DO THE NUMBERS MEAN?

Most people believe that a 5w30 oil is good for cold weather use because it is a "5 weight" oil in cold temperatures and a "30 weight" oil at high temperatures. On the surface this might seem to make a certain amount of sense. Naturally, a "5 weight" oil would flow better than a "30 weight" oil. This would make it ideal for cold temperature operation.

Nevertheless, this is a profound misunderstanding of what the labeling means. The two numbers really have little to do with each other. The final number based upon the kinematic viscosity at 100 degrees C, as we discussed for monograde oils.

So, if a multi-grade oil, when heated to 100 degrees C, falls within a certain kinematic viscosity it is classified as a certain SAE grade (the last number - like the "30" in 5w30). In other words, the kinematic viscosity of a 5w30 multi-viscosity oil falls within the same range at 100 degrees C as a monograde SAE 30 weight oil does.

A multi-viscosity oil also has to meet a "High Temperature/High Shear" requirement, but I'll talk about that in a minute.

The first number (the "5" in 5w30) is only a relative number which basically indicates how easily it will allow an engine to "turn over" at low temperatures. It is NOT a viscosity reference. In other words, a 10w30 is NOT a 10 weight oil in cold temperatures and a 30 weight oil in warm temperatures.

In fact, since SAE viscosity classifications only apply to an oil at 100 degrees C, it doesn't even make sense to label it as a certain SAE viscosity at any temperature other than 100 degrees C.

Besides, if you thought about it for a second, it wouldn't make sense for a 10w30 oil to be a 10 weight oil in the cold and a 30 weight oil in warm temperatures. What liquid do you know of that gets "thicker" as its temperature increases or "thinner" as the temperature decreases?

I would venture to say you probably can't come up with one. This holds true for motor oil as well. If a 10w30 was a 30 weight oil at 100 degrees C and a 10 weight oil at cold temperatures, that would mean it "thinned out" as the temperature dropped. That just doesn't make any sense considering what we know about liquids. It just doesn't happen like that.

The fact is that a 5w30 motor oil is thicker in cold temperatures than in warm temperatures. However, a 5w30 motor oil will be thinner than a 10w30 motor oil when subjected to the same low temperature conditions - because the "W" number is lower. This is an indication of better cold weather performance.

In other words, a 5w30 flows better in cold weather than a 10w30 motor oil will. Think of the "W" as a "winter" classification instead of a "weight" classification.

Results from the Cold Crank Simulator (CCS) and Mini-Rotary Viscometer (MRV) tests are used to determine the oil's "W" grade. The better the engine "startability" of the oil at low temperature, the lower the W classification. Each W grade must meet certain "startability" requirements at a specified temperature.

For instance, a 0W grade oil must have a maximum CCS centipoise (cP) value of 3250 @ -30 degrees C as well as a maximum MRV cP of 60,000 @ -40 degrees C. A 5W grade oil must have a maximum CCS cP value of 3500 @ -25 degree C and a maximum MRV cP of 60,000 @ -30 degrees C. The lower the cP value for both specifications, the better.

Notice that the 0W grade oil is tested at a lower temperature on both tests AND must still have a lower CCS cP value than a 5W oil which is tested at a higher temperature. As a result, a 0w30 will allow your vehicle to start easier on a cold morning than a 5w30 will. Likewise, a 5w30 oil will pump easier in cold temperatures than a 10w30 oil will.

Nevertheless, at 100 degrees C, they all fall within the same kinematic viscosity range. Therefore, they are all classified as SAE 30 weight oils at 100 degrees C. In other words, after your engine has warmed up, a 0w30 and 10w30 motor oil are basically the same thickness (within a certain SAE specified range).

Of course, although this is true when the oil comes out of the bottle, we'll see in the next section that, with petroleum oils at least, the viscosity that comes out of the bottle may not necessarily be the viscosity that you find within your engine after a short period of driving.

Multi-viscosity oils provide a great deal more flexibility to protect an engine over a wider temperature range than monograde oils do. Obviously, this should be considered a good thing. However, there is a drawback to multi-viscosity oils. When manufactured from a petroleum basestock, they tend to "shear" back very easily. In fact, this was already alluded to in the previous chapter.

You see, the waxy contaminants within petroleum basestocks crystalize in cold temperatures causing them to "thicken" and become hard to pump. So, in order to allow for good flow characteristics at low temperatures, in addition to using pour point depressant additives, petroleum oils must start with a very "thin" basestock.

For instance, let's look at a 5w30 motor oil. In order to flow well enough to meet the 5W classification, a petroleum oil would start with a very thin basestock (maybe one that would be classified as an SAE 20 weight oil if heated to 100 degrees C). Then, that basestock would be combined with pour point depressant additives.

Remember from the last chapter that these pour point depressants help the basestock maintain its low viscosity even at low temperatures. They counteract the crystallization of waxy contaminants in the oil.

Thus, the oil maintains it's viscosity instead of thickening up as the temperature drops. But, in order to meet the requirements to be classified as an SAE 30 oil, something must be done to assure that this oil won't thin out to it's 20 weight basestock viscosity at 100 degrees C. The oil must be "built up" using the long-chain, high-molecular-weight polymers (called Viscosity Index Improvers) discussed in the previous chapter.

These polymers expand as temperature increases counteracting the natural thinning action of heating an oil. So instead of thinning to a 20 weight classification, the oil only thins to a 30 weight classification.

NOTE: Remember, don't let the 5W fool you. It's not a viscosity classification. It's a classification to establish that an oil will flow adequately at cold temperatures to protect your engine. The oil is still

THICKER at cold temperature than it is at hot temperatures. The oil will thin as the temperature increases. The only question is how much. VI improvers reduce this thinning action to acceptable levels so the oil can meet both the 5W requirements and the SAE 30 requirements.

Now, let me just say that, the more you think about this issue of viscosity, the more your brain is going to hurt. Just remember that petroleum basestock viscosities are prone to significant change as the basestock is heated and cooled. As it cools, it "thickens" and as it heats it "thins".

To counteract that, petroleum oil manufacturers start with a basestock "thinner" than the "30" in "5w30" (or thinner than the "40" if they're manufacturing a 10w40 oil, etc.) and add pour point depressants so the oil stays as thin as possible in cold weather. Then they add viscosity index improvers that expand with increases in heat so that the oil will not thin out too much to meet the 30 weight classification at 100 degrees C. This is how they meet the multi-grade specification.

Unfortunately, long chain polymers (VI improvers) are more unstable the longer they are. The nature of petroleum basestocks necessitates that they be "built-up" using very long chain polymers. Therefore, these long chain polymers break down fairly quickly. In turn, over a short period of time, a 5w30 petroleum oil may actually "shear back" to a 5w20 (or lower) as these polymers break down. Obviously, this can lead to a decrease in engine protection.

For this reason, to assure at least a minimum amount of protection, the SAE J300 describes another requirement that a multi-viscosity oil must meet in order to be given its multi-viscosity classification. It must maintain a certain cP level on the High Temperature/High Shear (HT/HS) test (ASTM D 4683).

This test must be performed in order to label an oil as a certain multi-grade classification because automobile manufacturers use the physical requirement standards listed in the SAE J300 in order to establish which viscosity grades should be used in which vehicles. If automotive and lubricant manufacturers are not working off the same play book, it's your engine that's at risk.

But, let's get back to the HT/HS test. If the oil shears back too much on this high temperature test, it cannot be sold as a multi-grade oil. In fact, the test results from this test are very helpful in indicating the quality of the oil. Since they're required for achieving a certain SAE viscosity grade classification, the manufacturing company has the data. Make sure you get it.

The higher the HT/HS number the better because this indicates less shearing. Petroleum oils tend to have low HT/HS numbers which barely meet the standards set by the SAE J300 specifications.

Also, because the petroleum oils are made with a light weight basestocks to begin with, they tend to burn off easily in high temperature conditions which causes deposit formation and oil consumption.

As a result of excessive oil burning and susceptibility to shearing (as well as other factors) petroleum oils must be changed frequently.

The good news is, not all multi-viscosity oils shear back so easily. Synthetic oils contain basically no waxy contamination to cause crystallization and oil thickening at cold temperatures. In addition, synthetic basestocks do not thin out very much as temperatures increase.

So, pour point depressants are unnecessary AND higher viscosity basestock fluids can be used which will still meet the "W" requirements for pumpability. In other words, it might be possible to meet 5W requirements with a synthetic basestock that would be classified as a 25 or 30 weight oil at 100 degrees C. Hence, little or no VI improver additive would need to be used to meet the 30 weight classification while still meeting 5W requirements.

The result is that very little shearing occurs within synthetic oils because they are not "propped up" with viscosity index improvers (long chain polymers). There simply is no place to shear back to. In fact, this is easy to prove by just comparing synthetic and petroleum oils of the same grade. Synthetics will generally have significantly higher HT/HS numbers. Of course, the obvious result is that your oil remains "in grade" for a much longer period of time for better engine protection and longer oil life.


Specs exlained:

P/S/B = Petroleum or Synthetic or Synthetic Blend

Noack Volatility (DIN 51581) 250°C for 1 hour, % weight loss

API = Most Current American Petroleum Institute Specification(s)

TBN = Total Base Number (ASTM D-2896)

VI = Viscosity Index (ASTM D-2270)

4 Ball = Four-Ball Wear Test (ASTM D 4172) Scar diameter, mm

PP = Pour Point (ASTM D-97)

Phos = Phosphorus ppm

FP = Flash Point (ASTM D-92)

Zinc = Zinc ppm

FRP = Fire Point (ASTM D-92)

CCS = Cold Crank Simulator Apparent Visc. @ x°C, cP (ASTM D 5293)

HT/HS = High Temperature High Shear Viscosity (ASTM D-4683)

Ash % = Sulfated ash percentage of motor oil volume (ASTM D-874)
 
#26 ·
WOW "jrbartholomew" !!!
Now THAT is detailed data a person can REALLY sink their teeth into. Absolutely AWESOME !! Thank You a million times. (I'm still thinking this TerrainForum is too good to believe,,,,)

This is exactly the kind of material that I enjoy "wading through." -YUP, my lovely wife is right when she lovingly accuses me of "over-thinking" things. But that's okay. Some of us really want to know "the story behind the story."

I have always been uncertain, and even suspicious by the casual (-even reckless) references to such terms as shearing, VI improver, pour point depressant additive, basestock, etc. And sad to say trying to glean actual/factual meaningful data from motor oil advertising data is pretty hopeless.

Well, low and behold. This material you just submitted does an excellent job of explaining it all. And I'm really quite intrigued by the referenced testing tools/methods. Sounds totally valid.

At the risk of sharing too much unnecessary information I'll have to say this: What really got me to thinking seriously about whether or not a 0W30 might be "better" than a 0W20 (at least in theory) was my last used oil lab report from Blackstone. It showed a cST viscosity at 100c of 6.8. And that was with only 1700 miles on the oil !! According to the oil manufacturer's data, (QSUD) it should be 8.3. Granted, there was a "trace" of fuel detected, but no where near the "allowable" amount. So then I really wondered about possible VI improver long-polymer shearing,,, But still, with only 1700 miles on the oil ??? What the heck ! So then I reviewed the last six reports on our Impala, which always uses 5W30 synthetic. (either QSUD or M1 AFS) The cST's on it always run in the mid 9's to mid 10's. -just where I think they should be. (by the way, any day now I should have another test report on the 'nox)

And I'm certainly by no means discounting the importance and validity of the HT/HS test as measured in Centipoise. I'm just using the cST viscosity values as the only practical means of comparison, since those numbers seem to be the only data readily available to us, the general public.

Now, I realize that the measured oil viscosity at 100c (-probably about what it is in an operating engine, road speed, after it has had long enough to stabilize) is not the only thing that matters. In fact it is my belief that most significant importance of proper oil viscosity (and pressure, of course) is simply to ensure that there is an adequate supply volume to all lubricated parts. (yes I know, to also supply the piston head oil spray nozzles as well,,,) To me, the real bottom line critical factor in preventing any metal-to-metal contact between these moving parts (and sliding parts, such as cam lobes and followers,,) is in fact the oil's actual factual real world film strength !! And the only way I know to determine that is by lab testing. -literally torture testing the oil's film strength to the failure point and recording that point in pounds per square inch. (and there is somebody out there on the internet that has done a splendid job of that,,,)

Also, I'm not discounting the other important factors of continuous adequate oil supply volume in these automotive engine applications. -such as replenishing the oil film, and parts cooling. It is just that the extremely critical factor of oil film strength seems to never get mentioned in any typical discussion of "quality motor oil" and all the related items of detergents, dispersants, anti-oxidants, etc. etc.

Okay, so here I am sort of back where I started. (but hopefully much more educated,,) On this little 1.5L turbo Equinox engine, I still believe an oil viscosity at 100c should be at least 9 centistokes, and probably even 10 or 11. I have yet to come across any engineering, mechanical, or operation reason to believe otherwise. And if in the process I have to sacrifice a fraction of a mile per gallon in the interest of much superior engine wear protection, guess which option I will choose !!!

I think "we" have possibly been "sold a little BS" when we hear the phrase, "well these latest engines have tighter tolerances and must use these very light weight oils." Hmmmm,,,, back to my documentation of every internal engine part I researched between the 2017 malibu vs 2018 and later equinox being the exact same GM OEM part number. My next logical step would be to go visit my local engine machine shop, and see if all of the bearing clearances, etc. are the same. (yes I know the 'nox is the "LYX" and the malibu is "L-something else" but I think that is due to some differences in engine external parts, parts location, accessories, mounts, brackets,,,,-who knows what)

Hey everyone, Thank you so much for putting up with me, assuming you have read all the way to the bottom of this.
And Thanks for continuing this discussion !!
 
#28 ·
Looks like its time for me to eat an appropriate portion of Crow. About two weeks, (early in this thread) I had made this statement: "BTW, I am registered over at BITOG dot com, and not meaning to show any undue disrespect for that site, the truth is I find it extremely challenging to extract actual facts from all of the rampant opinions."

Well, I now must say that I have spent several hours over there pouring through all sorts of excellent material. -not the least of which I found by pressing the "home" button and reading an excellent document on the topic of the differences between base-stock oils. -also a couple of good articles on the upcoming "Generation 3" Dexos 1 motor oil spec.

And thank you "rednox301" for mentioning BITOG, as it prompted me to go over there and have a look around. I even participated in a couple of their threads.

Anyway, just wanted to let everyone know about the useful material I found over there.
 
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#30 ·
Time for an update: First, thank you Skip for your comment. Yes, the safest advice is to simply use exactly what the owners manual says. -especially while under warranty. And I'm sure that my Chevy Dealer would really prefer that I use their over-priced oil in the AC Delco blue bottles. -probably a very good oil made by Exxon/Mobil, and it is probably now a true synthetic oil. (but isn't it interesting how they still use Mobil 1 in their 'vettes, and maybe Camaros too?) As for me, my definition of the word safest might lean more in the direction of best for the engine in terms of the best long term wear protection.

So, here is where I am today. I purchased a couple 5 qt jugs of M1 Advanced Fuel Economy 0W30. I plan on using that oil from about April to October, pull a sample, and then study the UOA (used oil analysis) report. My reasoning for trying 0W30 is based on several things, including the very good material presented in this forum topic by jbartholomew. And also by Technical Article #56, in the extensive amount of good material presented by the mechanical engineer who has authored "Tech Facts NOT Myths." (any web browser search engine will find it).
In that tech article he points out numerous facts comparing 0W20 and 0W30. If I may present two brief quotes: "0W20 has a cold viscosity rating of a 0wt oil. 0W30 has a cold viscosity rating of a 0wt oil. So, being cold rated 0wt oils, and being synthetic oils, both have excellent cold flow capability, making them approximately equivalent in that regard." and then this: "But they are NOT equivalent in their hot operating temperature viscosity rating. 0W20 has hot viscosity rating of a 20wt oil. 0W30 has a hot viscosity rating of a 30wt oil."
In his many years of analyzing, testing, and very importantly applying what he has learned in many of his own and many friends and associates real world engine applications, he is 100% convinced that 30wt hot viscosity rated motor oils are the IDEAL VISCOSITY for most water cooled stock or modified gasoline engines. I purposely emphasize for most, because we can maybe find a couple of exceptions, m-a-y-b-e based on legitimate engineering factors, not just the possibility of some fractional reduction in internal friction due to dynamic viscosity, which --m-a-y----p-o-s-s-i-b-l-y-- result in a fractional increase in fuel efficiency.

Hey don't get my wrong, I love high gas mileage numbers as much as anyone. The most important factor for me is long term wear protection and overall health of the engines in all of my personal vehicles. I just LOVE reports of people getting 200,000 plus miles from today's ordinary vehicles. (and you can bet every one of them are also following excellent OCI practices, no matter what specific oil they use)

So, after spending all of this time exploring this very interesting rabbit hole, it leaves me with this decision: Be BRAVE and use 0W30, or chicken out and stay with 0W20.

Whatever I do, I will certainly continue to send in a sample for lab analysis and report from every oil change. And of course carefully compare results. In part it was noticing how low my 100 degree C viscosity numbers have been on this 1.5t engine using 0W20. On the other hand, my Impala 3.6L using 5W30 has always had excellent hot viscosity numbers right in the middle of where they should be.

Cheers to everyone !! Thanks for your interest in this topic, and your good replies.

So for me, that narrows it down to either 0W30 or 5W30. I just have to be BRAVE enough to give it a try.
 
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