What 5W-30 oil brand are you using for the 6.6L gas?

diyer2 · November 1, 2025

I would think the price of motor oil could be an indicator of quality. Amsoil OE line motor oil I use is $7.49 a quart, member price, they claim 100% synthetic. Price per quart goes up from there no matter the brand.

customboss · November 1, 2025

10 hours ago, Chuck FB said:

That strange, I had typed out a reply hours ago and perhaps I didn't hit submit.

In any event I did take a look at the pdf you linked as well as digging up the Coop website and took a bit of a look through the gas oils as well. I compared the few items they do list in the specs for both the Coop and Mobil heavy duty diesel 0W-40 and there are some differences, TBN was higher on the Mobil but also of note the Coop had a higher 100c viscosity. As to the gas rated oils, I guess of no surprise and Grumpy Bear has pointed out that aspect to me as per that whole Dexos theme of forcing formulators to produce low viscosity oils that barely meet grade and the Coop oils are no different with slightly lower viscosity out of the bottle vs some other brands within the Dexos theme. If I was past warranty I know what I would do and that would be to go with a Euro spec oil that is SP/LSPI friendly for this L8T DI engine and go with either a 5W-30 ( with around a 12 @ 100c ) or even a 5W-40 if I was towing, and then revert to a Euro 0W-30 for the winter.

Over the years the Canadian oil analysis customers that used the CO-OP fuels and lubricants consistently showed exceptional results vs running off the shelf stuff. I like buying local too. The Amsoil products are exceptional and you have a Canadian Amsoil depot in Canada.

Mobil is good but IMHO not best.

Viscosity only one measure but Grumpys diatribe about Viscosity leaves out alot. Beware.

Chuck FB · November 1, 2025

14 minutes ago, customboss said:

Over the years the Canadian oil analysis customers that used the CO-OP fuels and lubricants consistently showed exceptional results vs running off the shelf stuff. I like buying local too. The Amsoil products are exceptional and you have a Canadian Amsoil depot in Canada.

Mobil is good but IMHO not best.

Viscosity only one measure but Grumpys diatribe about Viscosity leaves out alot. Beware.

In a way its somewhat non logical that I tend to gravitate ( in more recent years that is due to the merger ) to Mobil but this all started many years ago with my dad having bought Texaco oil and then Imperial took over Texaco from what little I know about it but the bulk location stayed the same and then ExxonMobil takes over the same locations although there was that cross over of some Mobil products already being sold through as we knew it as "Esso". So here I am all these years later buying Mobil products where it used to be Texaco !.

The UFA is where we bought bulk fuel for a long time and still do although there was a period where I was going through Petro Canada due to being ripped off by the powers that be price gouging at UFA. But oil wise while I only bought a small amount of oil through Petro Canada or UFA, UFA used to get their own packaged oil and there was always the question mark about what quality of oil they were buying for their own brand and competitors were quick to point that out that it was a second line oil additive package and as a consumer its impossible to know what was actually in the bottle. So quite a few years ago now UFA dropped their own labeled oil and instead handle both Shell and Chevron which I imagine was a good move as Shell Rotella is a very popular oil as is Mobil Delvac , and I believe a lot of Petro Canada oil moves as well but its not a brand typically seen on store shelves for the small volume purchaser.

So where does Co-op fit around here, well in the past they didn't have much of a presence that I am aware of but they have built up quite a few fuel station locations, cardlock locations etc for highway tractors but nothing near me. I do see a tri drive Co-op fuel delivery truck drive by our farm so someone is buying their fuel but its that marketing perception of a bottle that says "Co-op" on the side of it vs a more well known brand name that I think gives a potential buyer pause, it does myself. Take the hot off the press news about Allison drawing to a close the use of their name on GM trucks, next June GM will no longer be able to use that well regarded name badging so that will not help sales, the reality is that a good name can hype up a poor product ... well at least my truck has the Allison name on it LOL.

Viscosity, obviously I am anything but an oil expert but based on the past with typical formulations having around that 12 viscosity at 100c, be that a 10W-30 or a 0W-30, while that still applies to the Euro spec oil, Dexos spec oil took quite a drop in viscosity and the talk ( and probably rightfully so ) of main stream oils sheering out of grade rather easily and compounding the problem with DI engines more prone to fuel dilution, that has me concerned. Then take the GM 6.2 engine issue and that really screams or at least to me as to the importance of viscosity if the engine is not perfectly machined as jumping from a 20 to a 40 grade is quite the jump and purely for its viscosity increase.

Chuck FB · November 1, 2025

2 hours ago, diyer2 said:

I would think the price of motor oil could be an indicator of quality. Amsoil OE line motor oil I use is $7.49 a quart, member price, they claim 100% synthetic. Price per quart goes up from there no matter the brand.

To a point I expect that is true but also could fall into the category of brand hype due to marketing prowess to create the hype. I liken it to some of these fashion brands that are beyond insanely expensive, womens purses that are many thousands of dollars or sun glasses by certain companies. Some of those products would be made inexpensively such as the sunglasses and then have a through the roof markup so that only the wealthy can afford it so is exclusive. I'll pick a brand like Royal Purple, is it really better than the others on the shelf as they certainly have jacked up prices here for it.

If I get around to it next week I want to try calling an Amsoil dealer in town and see if he even has a method/place of stopping by to physically buy anything. See, that is something people in larger cities in Canada or by the sounds of it most places in the USA even rural can get door delivery. Good luck with that out in locations like where I am as there are exactly zero delivery/shipping companies that go near my area, never mind would ever dream of going to someone's farm. I have to be able to physically go to the product and why a store front has and always will be my life line to anything other than bulk fuel where fuel companies will deliver due to the amount of funds being exchanged. There is no "just get X on Amazon" its just not happening.

Edited November 1, 2025 by Chuck FB

Grumpy Bear · November 1, 2025

2 hours ago, Chuck FB said:

Viscosity, obviously I am anything but an oil expert but based on the past with typical formulations having around that 12 viscosity at 100c, be that a 10W-30 or a 0W-30, while that still applies to the Euro spec oil, Dexos spec oil took quite a drop in viscosity and the talk ( and probably rightfully so ) of main stream oils sheering out of grade rather easily and compounding the problem with DI engines more prone to fuel dilution, that has me concerned. Then take the GM 6.2 engine issue and that really screams or at least to me as to the importance of viscosity if the engine is not perfectly machined as jumping from a 20 to a 40 grade is quite the jump and purely for its viscosity increase.

There is an published JASO MA/MA1 spec that concerns itself with shear stability (SSI). A minimum viscosity that in every case is lower than the SAE standard for the grade, new, in bottle. JASO also conducts the test requirement for a PCMO HTHS standard AFTER a 30 cycle Kurt Orbahn shear test. ILSAC, SAE and ACEA don't have this inclusion or at least none I can find. Be a bit cautious rooting around in these pages as there are some typo's not easy to spot. Nothing nefarious just sloppy editing.

https://www.lubrizol.com/company/specifications/jaso/jaso-ma1

The SSI test is also post Orbahn cycle as it is to reflects ONLY the permanent part of the VII polymers shear down.

In each case the JASO SSI value is one grade lower that the SAE/ACEA/ILSAC requirements for new PCMO per grade.

This is referred to as "Energy Conserving" It's how an SAE *W30 meets the fuel economy standards equating a SAE 20.

IF an OEM has a 'stay in grade' requirement it becomes the minimum. The JASO only points to the direction formulators use to pass energy conserving standards and the method used to acquire it. BUT stay in grade is again, only the permanent shear value (SSI)

Why is this of note? Because the temporary shear is even lower that the SSI index would indicate. I've posted Warren Oils in house lab sheet on this many times. I'll just post the highlight here...

SAE 5W30 COSTCO Signature

SAE requirement 9.3 to 12.5 cSt ( Data from SAE J300)

100 C viscosity result 10.91 cSt (Data from Warren Oil)

100 C viscosity SSI value is 9.4 cSt (Data from Warren Oil)

100 C viscosity HTHS value is 6.9 cp / .799 = 8.64 cSt or the lower end of a SAE *W20 (Data from Warren Oil)

(density reference for the above calculation from https://wiki.anton-paar.com/vn-vi/engine-oil/)

All of the above is the monkey motion of VM polymers. A really REALLY good idea to give us multigrade oils has been highjacked for another purpose. Fuel economy.

I've run 10W40 in Big Twin Harleys for decades and in part because I use HUGE coolers to limit oil temps thus viscosity loss. I showed one of my setups to a Harley Engineer who told me that what I was doing was something they would like to do BUT no self respecting Harley rider would even consider running anything but 20W50, 20W60. SAE 50 or 60. In other words if they tell the truth it hurts the bottom line.

So how do you get car guys to use a SAE 20? Make a *W30 that under shear IS an SAE 20.

customboss · November 1, 2025

2 hours ago, Chuck FB said:

To a point I expect that is true but also could fall into the category of brand hype due to marketing prowess to create the hype. I liken it to some of these fashion brands that are beyond insanely expensive, womens purses that are many thousands of dollars or sun glasses by certain companies. Some of those products would be made inexpensively such as the sunglasses and then have a through the roof markup so that only the wealthy can afford it so is exclusive. I'll pick a brand like Royal Purple, is it really better than the others on the shelf as they certainly have jacked up prices here for it.

If I get around to it next week I want to try calling an Amsoil dealer in town and see if he even has a method/place of stopping by to physically buy anything. See, that is something people in larger cities in Canada or by the sounds of it most places in the USA even rural can get door delivery. Good luck with that out in locations like where I am as there are exactly zero delivery/shipping companies that go near my area, never mind would ever dream of going to someone's farm. I have to be able to physically go to the product and why a store front has and always will be my life line to anything other than bulk fuel where fuel companies will deliver due to the amount of funds being exchanged. There is no "just get X on Amazon" its just not happening.

Right on!

customboss · November 1, 2025

12 minutes ago, Grumpy Bear said:

There is an published JASO MA/MA1 spec that concerns itself with shear stability (SSI). A minimum viscosity that in every case is lower than the SAE standard for the grade, new, in bottle. JASO also conducts the test requirement for a PCMO HTHS standard AFTER a 30 cycle Kurt Orbahn shear test. ILSAC, SAE and ACEA don't have this inclusion or at least none I can find. Be a bit cautious rooting around in these pages as there are some typo's not easy to spot. Nothing nefarious just sloppy editing.

https://www.lubrizol.com/company/specifications/jaso/jaso-ma1

The SSI test is also post Orbahn cycle as it is to reflects ONLY the permanent part of the VII polymers shear down.

In each case the JASO SSI value is one grade lower that the SAE/ACEA/ILSAC requirements for new PCMO per grade.

This is referred to as "Energy Conserving" It's how an SAE *W30 meets the fuel economy standards equating a SAE 20.

IF an OEM has a 'stay in grade' requirement it becomes the minimum. The JASO only points to the direction formulators use to pass energy conserving standards and the method used to acquire it. BUT stay in grade is again, only the permanent shear value (SSI)

Why is this of note? Because the temporary shear is even lower that the SSI index would indicate. I've posted Warren Oils in house lab sheet on this many times. I'll just post the highlight here...

SAE 5W30 COSTCO Signature

SAE requirement 9.3 to 12.5 cSt ( Data from SAE J300)

100 C viscosity result 10.91 cSt (Data from Warren Oil)

100 C viscosity SSI value is 9.4 cSt (Data from Warren Oil)

100 C viscosity HTHS value is 6.9 cp / .799 = 8.64 cSt or the lower end of a SAE *W20 (Data from Warren Oil)

(density reference for the above calculation from https://wiki.anton-paar.com/vn-vi/engine-oil/)

All of the above is the monkey motion of VM polymers. A really REALLY good idea to give us multigrade oils has been highjacked for another purpose. Fuel economy.

I've run 10W40 in Big Twin Harleys for decades and in part because I use HUGE coolers to limit oil temps thus viscosity loss. I showed one of my setups to a Harley Engineer who told me that what I was doing was something they would like to do BUT no self respecting Harley rider would even consider running anything but 20W50, 20W60. SAE 50 or 60. In other words if they tell the truth it hurts the bottom line.

So how do you get car guys to use a SAE 20? Make a *W30 that under shear IS an SAE 20.

You realize that people here don’t have the interest that you have in the science of shearers stability right. Plus, they have no access to data for a given product to know what it’s SSI permanent shear stability is permanent sheer loss. You know things that I did for a living that you’re just gonna lose people writing that stuff down. I know what you mean well grumpy but try to keep it simple man.

Chuck FB · November 1, 2025

24 minutes ago, Grumpy Bear said:

There is an published JASO MA/MA1 spec that concerns itself with shear stability (SSI). A minimum viscosity that in every case is lower than the SAE standard for the grade, new, in bottle. JASO also conducts the test requirement for a PCMO HTHS standard AFTER a 30 cycle Kurt Orbahn shear test. ILSAC, SAE and ACEA don't have this inclusion or at least none I can find. Be a bit cautious rooting around in these pages as there are some typo's not easy to spot. Nothing nefarious just sloppy editing.

https://www.lubrizol.com/company/specifications/jaso/jaso-ma1

The SSI test is also post Orbahn cycle as it is to reflects ONLY the permanent part of the VII polymers shear down.

In each case the JASO SSI value is one grade lower that the SAE/ACEA/ILSAC requirements for new PCMO per grade.

This is referred to as "Energy Conserving" It's how an SAE *W30 meets the fuel economy standards equating a SAE 20.

IF an OEM has a 'stay in grade' requirement it becomes the minimum. The JASO only points to the direction formulators use to pass energy conserving standards and the method used to acquire it. BUT stay in grade is again, only the permanent shear value (SSI)

Why is this of note? Because the temporary shear is even lower that the SSI index would indicate. I've posted Warren Oils in house lab sheet on this many times. I'll just post the highlight here...

SAE 5W30 COSTCO Signature

SAE requirement 9.3 to 12.5 cSt ( Data from SAE J300)

100 C viscosity result 10.91 cSt (Data from Warren Oil)

100 C viscosity SSI value is 9.4 cSt (Data from Warren Oil)

100 C viscosity HTHS value is 6.9 cp / .799 = 8.64 cSt or the lower end of a SAE *W20 (Data from Warren Oil)

(density reference for the above calculation from https://wiki.anton-paar.com/vn-vi/engine-oil/)

All of the above is the monkey motion of VM polymers. A really REALLY good idea to give us multigrade oils has been highjacked for another purpose. Fuel economy.

I've run 10W40 in Big Twin Harleys for decades and in part because I use HUGE coolers to limit oil temps thus viscosity loss. I showed one of my setups to a Harley Engineer who told me that what I was doing was something they would like to do BUT no self respecting Harley rider would even consider running anything but 20W50, 20W60. SAE 50 or 60. In other words if they tell the truth it hurts the bottom line.

So how do you get car guys to use a SAE 20? Make a *W30 that under shear IS an SAE 20.

In a word .. well two, Those Bastards ! ( it really is a slippery business ) as in the powers that be who dictate what product the chemists/engineers must come up with to meet a criteria without changing the viscosity numbers on the bottle.

This makes me think of back in the day when 10W-30 became a thing and yet diesel equipment manufacturers or so I felt were still leaning to straight grades as per 30 weight as the ambient temperature range on the provided chart in the operators manual for a 10W-30 was not near as high as it was for the straight 30 grade and I assume there was a reason for that as per how the multi viscosity oil on the market wasn't able to retain its properties to stay in grade. Perhaps why 15W-40 became the go to oil for diesel engines as it evolved due in part to expected sheer ?.

However are you saying that as time went on they had better oil formulation chemical technology as well as base stock but instead of making use of that to formulate a multi grade that would stay in grade, they purposely formulated oils that under use would temporarily sheer down even more than what a used oil viscosity test shows ?. I've always wondered what that energy conserving additive was and in fact your saying it was never a chemical at all but that the oil became thinner temporarily under stress ?. I know from years ago, be it a dirt bike or then a quad that Honda in this case was always warning not to use an oil that was energy conserving because it could cause the clutch to slip and I always related that to some slippery additive that the oil must be containing.

My brother has a 2009 Harley I believe it is, he has used it so little through the years but I am quite sure he is using the Harley oil which is probably not the ideal oil to be using, I am guessing the Amsoil 20W-50 ( a female ex heavy duty mechanic I know who has a Harley was mentioning lately that she uses the Amsoil for for her motorcycle as they are hard on oil being air cooled ) .

So the question is, what the heck is 0W-20 oil temporarily sheering down to or ... 0W-8 !

Grumpy Bear · November 1, 2025

9 hours ago, Chuck FB said:

However are you saying that as time went on they had better oil formulation chemical technology as well as base stock but instead of making use of that to formulate a multi grade that would stay in grade, they purposely formulated oils that under use would temporarily sheer down even more than what a used oil viscosity test shows ?. I've always wondered what that energy conserving additive was and in fact your saying it was never a chemical at all but that the oil became thinner temporarily under stress ?. I know from years ago, be it a dirt bike or then a quad that Honda in this case was always warning not to use an oil that was energy conserving because it could cause the clutch to slip and I always related that to some slippery additive that the oil must be containing.

My brother has a 2009 Harley I believe it is, he has used it so little through the years but I am quite sure he is using the Harley oil which is probably not the ideal oil to be using, I am guessing the Amsoil 20W-50 ( a female ex heavy duty mechanic I know who has a Harley was mentioning lately that she uses the Amsoil for for her motorcycle as they are hard on oil being air cooled ) .

So the question is, what the heck is 0W-20 oil temporarily sheering down to or ... 0W-8 !

Yes.

Two things can be true at the same time but yes, thinner and yet some chemistries are indeed 'slicker'. A bit of POE in a PAO adds lubricity. Whale oil, now outlawed, did the same. Castor Bean oils had their time. But other things too. Moly. Borated esters and so on. Clutch issues were more likely caused by Moly, graphite and the like.

0W8 to 0W20 is less shear prone. Whaaaaat? Because the bases used to make them are naturally or nearly so already in grade and as such need zero to very little VII polymers and when they do, ones of very small molecular weight. That is, not much chain length to shear down. When you are making a *W20 from a Group III, i.e., those bases generally range in viscosity between 4 and 8 cSt naturally covering the SAE *W8 to *W20 range. Thus can be formulated neat or nearly so. When you are making an SAE 30 it needs some help and if you are making an SAE 40 or SAE 50 it needs allot of help.

Sometimes that help comes from VM's and sometimes it comes from blending other base types that have higher viscosity ceilings. A Group II will cover 4 to 30 cSt. m-POA hundreds and esters are built to suit.

There are *W30's that stay 30's. Just not ILSAC G6 or Dexos1Gen* oils. Those that are have designations like Dexos2, ACEA C3 or A3/B4 (depending on ash and ZDP load). No-VII oils, Naturally straight grades. High end oils made of Group's IV and V ONLY. (m-POA, Di-Ester, Polyol Esters, AN's)

Find and look at some Pennzoil GTL based or Shell Helix 0W40 VOA v UOA's and see how far they will shear down. GTL has a very narrow range. Something like 2 to 4 cSt.

Terry is right about there being more to oil that its viscosity but it is the most important aspect of a lubricant. We could talk about those other things if one would stop shouting "Don't look at that". LOL

Edited November 2, 2025 by Grumpy Bear

Chuck FB · November 1, 2025

14 minutes ago, Grumpy Bear said:

Yes.

Two things can be true at the same time but yes, thinner and yet some chemistries are indeed 'slicker'. A bit of POE in a PAO adds lubricity. Whale oil, now outlawed, did the same. Castor Bean oils had their time. But other things too. Moly. Borated esters and so on. Clutch issues were more likely caused by Moly, graphite and the like.

0W8 to 0W20 is less shear prone. Whaaaaat? Because the bases used to make them are naturally or nearly so already in grade and as such need zero to very little VII polymers and when the do ones of very small molecular weight. That is, not much chain length to shear down. When you are making a *W20 from a Group III, i.e., those bases generally range in viscosity between 4 and 8 cSt naturally covering the SAE *W8 to *W20 range. Thus can be formulated neat or nearly so. When you are making an SAE 30 it needs some help and if you are making an SAE 40 or SAE 50 it needs allot of help.

Sometimes that help comes from VM's and sometimes it comes from blending other base types that have higher viscosity ceilings. A Group II will cover 4 to 30 cSt. m-POA hundreds and esters are built to suit.

There are *W30's that stay 30's. Just not ILSAC G6 or Dexos1Gen* oils. Those that are have designations like Dexos2, ACEA C3 or A3/B4 (depending on ash and ZDP load). No-VII oils, Naturally straight grades. High end oils made of Group's IV and V ONLY. (m-POA, Di-Ester, Polyol Esters, AN's)

Find and look at some Pennzoil GTL based or Shell Helix 0W40 VOA v UOA's and see how far they will shear down. GTL has a very narrow range. Something like 2 to 4 cSt.

Terry is right about there being more to oil that its viscosity but it is the most important aspect of a lubricant. We could talk about those other things if one would stop shouting "Don't look at that". LOL

You're last comment first, LOL ... its all good as even if myself or others only grasp a little of the complicated topic of oils that either Terry or yourself know a lot about but may have a different method of explaining it but to a similar end, it still helps the average person realize that not all formulations are the same, nor is those designated multi grade numbers on the side of the bottle necessarily match to what its physical properties perform like in use.

I recall Lake Speed mentioning GTL within certain videos and again with what he gets into sometimes becomes a little over ones head for sure and yet its easy to see his audience gets very engaged to learn what they can grasp of what he tries to relay but those that are not interested would never watch his videos. And that is how I view topics like this talked about on a forum, not everyone will be interested and so they pass it over to read something else they are more interested in.

Speaking of the additives not good for clutches like Moly etc, I now realize that is 20 years ago when I would have called up Exxon in Ontario to speak to an oil specialist about using Mobil Delvac 0W-40 in my honda quad with the lovely hydrostatic transmission and it has the centrifugal clutch. At that time anyway he said it was quite fine to use, and here I am 20 years later using the same theme of oil but honestly I don't know if the newer blends of that oil are really condoned to be used in that application now.

I've said as well before that I have older vehicles and gas tractors etc, all of those items would have been made at a time when zinc was at much higher levels in oil and yet to get a true year around flowing oil it makes sense to use a 0W-30, and that too is why I wonder if as per on an easily obtainable oil theme if a Euro spec Dexos 2 0W-30 oil would be the better choice over the Dexos 1 thinner viscosity oils. I don't know where the zinc and other complementary chemistry lies for flat tappet cam between the two specs. Over the last years I have sometimes used a bit of GM additive which I would have to look at the bottle but its for "classic" vehicles and is meant as an additive which unfortunately also means I am being a clueless chemist by adding anything to an existing oil. I would much rather just use an oil that is suitable and not play with fire as isn't that how the kid in school has something blow up in their face in chemistry class ?

Grumpy Bear · November 2, 2025

6 hours ago, Chuck FB said:

isn't that how the kid in school has something blow up in their face in chemistry class ?

It is :crackup:

6 hours ago, Chuck FB said:

if a Euro spec Dexos 2 0W-30 oil would be the better choice over the Dexos 1 thinner viscosity oils.

Dexos oils of any spec will not have enough anti-wear for old flat tappet iron which makes viscosity mut. You have entered the world of boutique products as the majority of the common market has left that segment in a ditch somewhere. Red Line HP, AMSOIL, Joe Gibbs Racing, TORCO, Penrite and Lucus Oil I believe have products for those applications. None of them will carry a Dexos license. Is there a product on a store shelf with an ACEA A3/B4 certification? :dunno: Ravenol? But it still wont carry a Dexos approval.

Grumpy Bear · November 2, 2025

Chuck FB · November 2, 2025

7 hours ago, Grumpy Bear said:

It is

Dexos oils of any spec will not have enough anti-wear for old flat tappet iron which makes viscosity mut. You have entered the world of boutique products as the majority of the common market has left that segment in a ditch somewhere. Red Line HP, AMSOIL, Joe Gibbs Racing, TORCO, Penrite and Lucus Oil I believe have products for those applications. None of them will carry a Dexos license. Is there a product on a store shelf with an ACEA A3/B4 certification? Ravenol? But it still wont carry a Dexos approval.

That right there is valuable information, to beware that a Dexos compatible oil won't meet the needs of a flat tappet cam engine. Keep in mind these older engines certainly don't need an SP rated oil as they lived just fine on oils with ratings from years ago but had far more zinc. So for example would the current Mobil Delvac1 0W-40 oil be one that would protect the flat tappets as I hope so as we have a lot of diesel engines around that have been using either that or for spring to fall use the 15W-40 Super 1300. I have been using the 10W-30 Super 1300 in some older gas engines that don't get used during the winter. So if the 0W-40 could protect well enough that could cover some of my needs but if I want to find a 0W-30 which typically does have a bit better low temp properties, would one of the Euro spec oils of lets say Mobil or Pennzoil etc that is easily found be sufficient.

I was trying to think of the newest example of a gas engine with a flat tappet around here and that probably would be my brothers early 2000's Jeep TJ with the 4.0 engine and it would have cats on it ( the Elite 222 has been run in it for years though ), and aside from that vehicle, various trucks with varying vintages of the GM 350, a Ford with the 300ci inline 6 and then these older gas tractor engines.

The big picture of what I have in front of me is "one" truck engine that according to GM requires Dexos approved oils because of the LSPI and the underlying bs as you explained with an oil thinner than its Dexos label would imply, everything else I have works just fine on last centuries oils.

Grumpy Bear · November 2, 2025

32 minutes ago, Chuck FB said:

if I want to find a 0W-30 which typically does have a bit better low temp properties, would one of the Euro spec oils of lets say Mobil or Pennzoil etc that is easily found be sufficient.

IMHO, no. Why? licensing requirements of current oils will prohibit sufficient ZDP levels for those motors.

As far as diesel oils in gas motors.... there are some issues there as well. Under SL levels of anti-wear (ZDP)and even if one could be found it is not a ZDP is of the same reactivity; read that availability. Dispersant and acid packages are quite different.

You're going to keep asking if there is a shelf oil for a flat tappet motor with current licensing and I'm going to keep saying no. Your looking for something with a API SL/SJ rating and the only places you will find those that I'm aware of is in the boutiques. A new motor would need even higher levels and a well broken in one perhaps, maybe, would do okay on an SM oil. I wouldn't but some would, have and have gotten away with it. Ditto diesel oil. Most of those have SM levels of anti-wear.