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

Chuck FB · September 22, 2025

On 9/21/2025 at 8:54 AM, Grumpy Bear said:

I belong to another car site for one of my other marks who has a large Canadian population. I see allot of these fellas actually have a spring/fall switchover maintenance routine that includes a change in oil grade. Temperature swings in your area seem to make it necessary.

Here is an example of 5W-40 or in the one case 0W-40 European spec oils in Canadian tire, the sites information for each oil may be out of date on their website but here are the links to these ones and I have not looked into if each one is Dexos comparable as in the low speed preignition aspect . Also they do have some 5W-30's as well as 0W-30 and yes some 0W20 as well in the Euro spec. This will give you an idea of some of what is easy to get ones hands on here for the foreign cars.

https://www.canadiantire.ca/en/pdp/mobil1-full-synthetic-euro-5w40-motor-oil-4-73-l-0289808p.0289808.html?rq=euro+engine+oil&colorCode=VISCOSITY_GRADE_CD_5w-40

https://www.canadiantire.ca/en/pdp/pennzoil-platinum-euro-5w40-synthetic-engine-motor-oil-5-l-0289358p.html?rq=euro+engine+oil

https://www.canadiantire.ca/en/pdp/castroledge-euro-a3-b4-5w40-synthetic-engine-motor-oil-5-l-0289225p.html?rq=euro+engine+oil

https://www.canadiantire.ca/en/pdp/motomaster-oeplus-european-premium-0w40-synthetic-engine-motor-oil-5-l-0287963p.html?rq=0W-40+engine+oil

Chuck FB · September 24, 2025

Since we were talking about engine oil and Dexos approved oil to cover warranty, this may not be the correct area of this forum to get into this but I had a comment from a service advisor at the dealership ( I was not getting any maintenance done ). The conversation was about the 2 complementary GM oil changes that I have not been taking advantage of as I am using a different oil and to be honest I am not thrilled with having maintenance done by people they just dragged off the street and stuffed into the oil service bay anyway. So the service advisor was asking, are you getting your engine oil changes done at another shop and I said no, I am doing them myself. Then he says well there was this customer who was doing his own maintenance and his engine had a failure and GM denied the warranty claim because he didn't have proof from a shop that the oil had been changed. He said call GM Canada themselves and that is what I did and I was told that GM Canada can deny the warranty if there is no proof from a shop record of oil changes. I said I have the receipts from the oil filters bought at the dealership as well as the oil I have purchase elsewhere but no, that is not proof enough.

So my question is, is this different in the United States as she had no idea what the states rules were, only what GM Canada claims in their warranty. Needless to say I am not impressed at all as I had no idea they could easily deny a claim because the work was done privately, I assume that would apply to any other maintenance as well performed on a transmission, diffs, even changing the fuel filter on a diesel truck ... no record, to bad ...

I was not able to get in contact with the service manager or warranty manager at the dealership to have a chat about this but will try to reach someone to see what the dealerships stance is on this.

Pryme · September 24, 2025

39 minutes ago, Chuck FB said:

Since we were talking about engine oil and Dexos approved oil to cover warranty, this may not be the correct area of this forum to get into this but I had a comment from a service advisor at the dealership ( I was not getting any maintenance done ). The conversation was about the 2 complementary GM oil changes that I have not been taking advantage of as I am using a different oil and to be honest I am not thrilled with having maintenance done by people they just dragged off the street and stuffed into the oil service bay anyway. So the service advisor was asking, are you getting your engine oil changes done at another shop and I said no, I am doing them myself. Then he says well there was this customer who was doing his own maintenance and his engine had a failure and GM denied the warranty claim because he didn't have proof from a shop that the oil had been changed. He said call GM Canada themselves and that is what I did and I was told that GM Canada can deny the warranty if there is no proof from a shop record of oil changes. I said I have the receipts from the oil filters bought at the dealership as well as the oil I have purchase elsewhere but no, that is not proof enough.

So my question is, is this different in the United States as she had no idea what the states rules were, only what GM Canada claims in their warranty. Needless to say I am not impressed at all as I had no idea they could easily deny a claim because the work was done privately, I assume that would apply to any other maintenance as well performed on a transmission, diffs, even changing the fuel filter on a diesel truck ... no record, to bad ...

I was not able to get in contact with the service manager or warranty manager at the dealership to have a chat about this but will try to reach someone to see what the dealerships stance is on this.

I have heard Canada is like that. Here in the states, the owner can do their own maintenance. Keeping your receipts just in case is the best idea.

Homer1959 · September 24, 2025

When i was doing the maintenance on my other vehicule i was also taking picture of my installation and product used including tools , ramp etc etc, a short video was also done while the oil was draining ... Who told you that i am paranoid ? ... I decided to take advantage of the 2 free oil change well 3 if i pay the fourth one just to play safe or just to take away some of their argument. Anyway i am not planning to keep the truck longer than the GM protection plan of 7 years or 100000km

Chuck FB · September 25, 2025

34 minutes ago, Homer1959 said:

When i was doing the maintenance on my other vehicule i was also taking picture of my installation and product used including tools , ramp etc etc, a short video was also done while the oil was draining ... Who told you that i am paranoid ? ... I decided to take advantage of the 2 free oil change well 3 if i pay the fourth one just to play safe or just to take away some of their argument. Anyway i am not planning to keep the truck longer than the GM protection plan of 7 years or 100000km

That's a good idea if I think about it, to take photos of km on the dash and the jugs of oil and filter I will put on etc. Of course there is no way of proving even with that, that the work has been performed. But on the other hand I would know that the plug isn't about to fall out ( or be stripped out ) or the filter fall off after I did the work, or that the plastic bodied air filter that the screws go into are not all stripped out and that a filter is actually in the housing if they touched that. The fact is most places count on their employees to do fast paced work in a oil change bay to slam the vehicles though.

Homer1959 · September 25, 2025

18 minutes ago, Chuck FB said:

That's a good idea if I think about it, to take photos of km on the dash and the jugs of oil and filter I will put on etc. Of course there is no way of proving even with that, that the work has been performed. But on the other hand I would know that the plug isn't about to fall out ( or be stripped out ) or the filter fall off after I did the work, or that the plastic bodied air filter that the screws go into are not all stripped out and that a filter is actually in the housing if they touched that. The fact is most places count on their employees to do fast paced work in a oil change bay to slam the vehicles though.

Chuck I fully understand you, im fighting with myself to let go. I have very little confidence when its time to have some work done by perfect stranger, im maybe naive but for the next 7 years max , its my truck but its their problem. Im far from being rich but i can afford to let go. Time will tell but ill be 73 when the truck will go away , whatever the result of my decision it wont have a big Impact On my future lol

Chuck FB · September 25, 2025

6 minutes ago, Homer1959 said:

Chuck I fully understand you, im fighting with myself to let go. I have very little confidence when its time to have some work done by perfect stranger, im maybe naive but for the next 7 years max , its my truck but its their problem. Im far from being rich but i can afford to let go. Time will tell but ill be 73 when the truck will go away , whatever the result of my decision it wont have a big Impact On my future lol

Sad but true as time goes on for all of us, we are looking more in the rear view mirror and less ahead as the clock doesn't stop ticking. I don't fault someone for wanting to take a step back and let someone else deal with the maintenance and you have an exit plan ( for your truck that is ! LOL ) where my plan although of course could change drastically, would be to hang onto the truck for a number of years and who knows what will be left of it then but the odds are the five year time will be up for the drive train before the km are reached. But that is why I want to try and keep on top of it for engine oil changes and for that matter the trans ( if I am able to ) and transfer case and diffs. Of course on the other hand I may be pushing up daisies a lot sooner than I realize but then I won't have to worry about my truck so that works out good actually ... LOL.

revrnd · September 25, 2025

On 9/21/2025 at 10:54 AM, Grumpy Bear said:

I belong to another car site for one of my other marks who has a large Canadian population. I see allot of these fellas actually have a spring/fall switchover maintenance routine that includes a change in oil grade. Temperature swings in your area seem to make it necessary.

Did they say in what part of Canada they lived in? I've lived in Southern Ontario all my life. In the 40+ years of truck ownership, I've never heard of switching viscosity for the winter (or vice versa). Until 2011, I lived about 70 miles N of Buffalo, so it's not like I lived on the edge of the tundra. Now I'm about 2 hours NE of the GTA.

I do recall maybe in the 90s(?) Petro-Canada introducing a 0W30 grade oil for the colder parts of Canada. My trucks have always had a block heater & that has worked when needed for me. If you've done any travel in northern Ontario (& I imagine other provinces), company parking lots provide plug in for block heaters.

Edited September 25, 2025 by revrnd

Grumpy Bear · September 25, 2025

10 hours ago, revrnd said:

Did they say in what part of Canada they lived in? I've lived in Southern Ontario all my life. In the 40+ years of truck ownership, I've never heard of switching viscosity for the winter (or vice versa). Until 2011, I lived about 70 miles N of Buffalo, so it's not like I lived on the edge of the tundra. Now I'm about 2 hours NE of the GTA.

I do recall maybe in the 90s(?) Petro-Canada introducing a 0W30 grade oil for the colder parts of Canada. My trucks have always had a block heater & that has worked when needed for me. If you've done any travel in northern Ontario (& I imagine other provinces), company parking lots provide plug in for block heaters.

No, I do not know where.

revrnd · September 26, 2025

15 hours ago, Grumpy Bear said:

No, I do not know where.

I see

Looking @ my manual, I saw this:

I dont recall seeing this concerning past trucks. It may have been in the manuals, but I ignored it since it didnt apply to me.

I wonder if this recommendation is more for trucks that aren't able to utilize a block heater which comes on @ -18* C/ 0* F?

Edited September 26, 2025 by revrnd

davester · September 26, 2025

My '12 3500 has that same recommendation in the owners manual (different wording), my '04 3500 says to use either 5w30 synthetic or 0w30 below -20f/-29c

Homer1959 · September 26, 2025

that bother me that 0w40 is not recommended , Im maybe not rational but I like how this oil fit the winter and the hot summer month especially for a working truck

KARNUT · September 26, 2025

Without all the science. A normal non machnical person would summarize. If a certain oil gives better fuel mileage it’s created less friction. Less friction less wear. Less wear longer life.

Homer1959 · September 26, 2025

9 minutes ago, KARNUT said:

Without all the science. A normal non machnical person would summarize. If a certain oil gives better fuel mileage it’s created less friction. Less friction less wear. Less wear longer life.

I like to believe that the oil will have more chance to die as a 30 than as a 20

Chuck FB · September 26, 2025

1 hour ago, KARNUT said:

Without all the science. A normal non machnical person would summarize. If a certain oil gives better fuel mileage it’s created less friction. Less friction less wear. Less wear longer life.

That would be probable if two equal viscosity @ operating temperature oils were being run and one showed a better fuel mileage for example. However in reality its the viscosity at operating temperature ( and at initial startup as well ) of a thin oil that causes less rotational drag between the moving shafts and its plain bearings and the piston/piston rings and the cylinder walls, a thinner oil in the bearings of the camshaft lifter rollers, less oil thickness on the camshaft for the lifter roller to push out of the way, the oil pump having less work to do as the oil is so thin to both suck and then push through the oil galleries, the timing chain and gears can squeeze out the excess oil easier ( less power required ) the thinner the oil is.

Use a thicker oil at operating temperature and up goes the parasitic drag loss.

However neither of those scenarios of thin oil vs thick oil even though the thin oil will show higher power output ( engine work ) from the engine for a given amount of fuel used and why these vehicle manufactures are pushing thin oils actually show which one protects the engines parts from contact friction. That's where the lab oil testing comes into play and what additives as well as viscosity do the best job at protecting all the parts from contacting each other and causing the least amount of wear and from testing I've seen done from lets say its a mechanic with a youtube channel testing different oils and may not be 100% scientifically accurate repeatable conditions ... to someone like a testing facility that Lake Speed has access to their lab and they test oils, often the results lean towards the thin oils not protecting as well as a somewhat thicker viscosity oil as long as the friction chemistry is equivalent. I use Lake Speed as the example as its not like there are tribologists coming out of the wood work showing test results from lab testing.

Two items that make one question the thin viscosity theme, GM coming out with their scheme of authorizing the use of 0W-40 in the years of the affected 6.2 engine as they would not have done that if they didn't think the thicker oil was not going to help keep the crankshaft from dragging on its plain bearings. Or that while half ton pickups typically are calling for 0W-20, most heavy duty gas trucks call for 5W-30 or I believe the Hemi 6.4 recommends 5W-40 or at least they used to. If the thin oil was the new "it" miracle oil, they would have no reason not to recommend it in the HD trucks but they don't for a reason, of course the manufactures certainly don't tell us what that reason is because if they did that might put a little cloud over the thin oil theme.