Why is it NOT OK for 0w40 in GM 5.3 engine?

[zogg]

I have a 2024 Sierra 5.3 with a Carbyte dfm disabler and I’m using Mobil 1 FS 0w40 and a Mobil 1 oil filter.
I opted for the 0w40 to hopefully protect the lifter assembly, though I’m not sure anything will help, and I’m not a believer in 0w20 oil. My theory is that since the valve/lifter assembly is the same as the 6.2, since GM is using 0w40 in it, then it should be good for the 5.3.
Anyway, folks have told me that I’m wearing out the oil pump, the lifter oil holes are too small, and the overall drag on the engine will cause premature wear.
Also, my gas mileage will be abysmal…but I’m getting 21+ mpg on the hiway at 78-80 mph, and the same 16-17 mpg around town.
So, I thought I’d ask you experts!! Should I stay with the 0w40 or back down to 0w30 or 5w30? Those are the recommendations I’ve received, as well as returning to the water like 0w20. Any advice is appreciated

 

[kschachn]

I have a 2024 Sierra 5.3 with a Carbyte dfm disabler and I’m using Mobil 1 FS 0w40 and a Mobil 1 oil filter.
I opted for the 0w40 to hopefully protect the lifter assembly, though I’m not sure anything will help, and I’m not a believer in 0w20 oil. My theory is that since the valve/lifter assembly is the same as the 6.2, since GM is using 0w40 in it, then it should be good for the 5.3.
Anyway, folks have told me that I’m wearing out the oil pump, the lifter oil holes are too small, and the overall drag on the engine will cause premature wear.
Also, my gas mileage will be abysmal…but I’m getting 21+ mpg on the hiway at 78-80 mph, and the same 16-17 mpg around town.
So, I thought I’d ask you experts!! Should I stay with the 0w40 or back down to 0w30 or 5w30? Those are the recommendations I’ve received, as well as returning to the water like 0w20. Any advice is appreciated

This again. Will this never end? None of that is even close to being accurate, it is complete Internet mythology.

The fuel economy differences between grades is about 1% to 2% maximum per grade.

A higher HT/HS helps protect the engine, not the other way around.

 

[JavierH19]

Anyway, folks have told me that I’m wearing out the oil pump, the lifter oil holes are too small, and the overall drag on the engine will cause premature wear.
Also, my gas mileage will be abysmal…but I’m getting 21+ mpg on the hiway at 78-80 mph, and the same 16-17 mpg around town.

Ok. So stupid people exist and thus will say stupid people things, what of it?

 

[Sam_Julier]

Stay with a 40 weight oil for the higher HTHS viscosity.

 

[oil pan 4]

I have a 2024 Sierra 5.3 with a Carbyte dfm disabler and I’m using Mobil 1 FS 0w40 and a Mobil 1 oil filter.
I opted for the 0w40 to hopefully protect the lifter assembly, though I’m not sure anything will help, and I’m not a believer in 0w20 oil. My theory is that since the valve/lifter assembly is the same as the 6.2, since GM is using 0w40 in it, then it should be good for the 5.3.
Anyway, folks have told me that I’m wearing out the oil pump, the lifter oil holes are too small, and the overall drag on the engine will cause premature wear.
Also, my gas mileage will be abysmal…but I’m getting 21+ mpg on the hiway at 78-80 mph, and the same 16-17 mpg around town.
So, I thought I’d ask you experts!! Should I stay with the 0w40 or back down to 0w30 or 5w30? Those are the recommendations I’ve received, as well as returning to the water like 0w20. Any advice is appreciated

People don't even remotely understand how a vehicle oiling system work.

 

[Sam_Julier]

People don't even remotely understand how a vehicle oiling system work.

Not sure of your point. Are you implying that a 0W-40 Euro spec oil with a 3.8 HTHS vis will damage a 5.3? Thanks.

 

[RBT]

whomever told you about the passages and what not - it is inaccurate. That being said, I don’t know the precise failure mechanisms of this engine but if the underlying issues are metallurgical, oil will not really address the issue. By analog, there were issues with lifters on hemi engines up until maybe the late teens when the supplier was changed to address. The popular Ram forums typically blamed the lighter viscosity synthetics (eg 5w20) instead of understanding that the underlying problem was metallurgical. Once Ram revised the part to address the issue, the problem went away for the vast majority of vehicles. All a long way of saying a 40 certainly won’t hurt anything and will provide a cushion if you are running high oil temps to better protect the engine but I am always wary of people stating that some of these issues can be addressed via oil. Typically that is not the case - there is an underlying defect and the oil is not the driver, so to speak. Good luck with your truck, hope the postings here are helpful.

 

[oil pan 4]

Not sure of your point. Are you implying that a 0W-40 Euro spec oil with a 3.8 HTHS vis will damage a 5.3? Thanks.

Not at all. 40wt is only a tiny bit thicker than 30wt when warmed up.

 

[GRUMPYDUDE2]

Stay with a 40 weight oil for the higher HTHS viscosity.

This!!

 

[Rand]

Ok. So stupid people exist and thus will say stupid people things, what of it?

Surprised the OP has been here for 17 years and started this post.

 

[User_19876]

I have a 2024 Sierra 5.3 with a Carbyte dfm disabler and I’m using Mobil 1 FS 0w40 and a Mobil 1 oil filter.
I opted for the 0w40 to hopefully protect the lifter assembly, though I’m not sure anything will help, and I’m not a believer in 0w20 oil. My theory is that since the valve/lifter assembly is the same as the 6.2, since GM is using 0w40 in it, then it should be good for the 5.3.
Anyway, folks have told me that I’m wearing out the oil pump, the lifter oil holes are too small, and the overall drag on the engine will cause premature wear.
Also, my gas mileage will be abysmal…but I’m getting 21+ mpg on the hiway at 78-80 mph, and the same 16-17 mpg around town.
So, I thought I’d ask you experts!! Should I stay with the 0w40 or back down to 0w30 or 5w30? Those are the recommendations I’ve received, as well as returning to the water like 0w20. Any advice is appreciated

Ask them which will damage your engine faster: a 20 or 30 grade at 10F, or a 40 grade at 90F.

 

[Kira]

So I Googled this thing. It's a plug-in gizmo which goes into the OBD port.
It disables Active / Dynamic fuel management systems....so the engine runs "normally".
It also disables "start-stop".
I don't know how this cylinder deactivation works.....
....but, if the engine runs normally, where does this concern for wear come from?

 

[zogg]

Thanks to all for the replies. I based my original decision to use the 0w40 on some info I got on this site. But a few mechanics and service folks said I was wrong.
I appreciate your expertise and I’m totally comfortable with the 0w40. The FS version is now SQ certified and supposed to be Dexos R approved. Looks like a winner to me!!

 

[GRUMPYDUDE2]

Thanks to all for the replies. I based my original decision to use the 0w40 on some info I got on this site. But a few mechanics and service folks said I was wrong.
I appreciate your expertise and I’m totally comfortable with the 0w40. The FS version is now SQ certified and supposed to be Dexos R approved. Looks like a winner to me!!

Thanks to all for the replies. I based my original decision to use the 0w40 on some info I got on this site. But a few mechanics and service folks said I was wrong.
I appreciate your expertise and I’m totally comfortable with the 0w40. The FS version is now SQ certified and supposed to be Dexos R approved. Looks like a winner to me!!

"Looks like a winner to me!"
It is!