Oil weight for 5.3? 0-20 no good?

[jerry455]

I have been running 0W30 in my 2021 6.2 Suburban for quite a while now with no problems.

 

[DuraYuk]

Boom.

https://gmauthority.com/blog/2025/05/should-you-use-0w-40-oil-in-your-non-recalled-gm-6-2l-l87-engine/

 

[Gearz]

5W-30 End of story. All these years we were told not to change the viscosity and guess what it was a LIE. Small changes are fine just don't use a 10W-50 in a 0W-20 engine. It's all so the manufacture can squeeze out the mileage criteria! I worked for a dealer on the line for 30 plus years and we never did a oil analysis to see if the correct oil weight was used!

 

[vcode]

5W-30 End of story. All these years we were told not to change the viscosity and guess what it was a LIE. Small changes are fine just don't use a 10W-50 in a 0W-20 engine. It's all so the manufacture can squeeze out the mileage criteria! I worked for a dealer on the line for 30 plus years and we never did a oil analysis to see if the correct oil weight was used!

Yet there are millions of 5.3L's out there that have traveled billions of miles on 0W20 with no issues. Go figure......

 

[viven44]

I think on a 5.3L we are talking about 200K+ miles with 0W-20 vs 300K+ with 5W-30.

Either option will obviously work and get a lot of miles, but it doesn’t change the fact that 5W-30 in GMs own words on oil viscosity that a thicker oil will offer “an enhanced further level of protection” than 0W-20.

 

[vcode]

I think on a 5.3L we are talking about 200K+ miles with 0W-20 vs 300K+ with 5W-30.

Either option will obviously work and get a lot of miles, but it doesn’t change the fact that 5W-30 in GMs own words on oil viscosity that a thicker oil will offer “an enhanced further level of protection” than 0W-20.

On 6.2L's with possible defective parts. Show me where it says that about 5.3's.

 

[15burban]

There's plenty of used oil analysis that shows that 5w30 has less wear then 0w20 or 5w20. I'm on a ram forum and the same topic gets brought up all the time. They even have one thread dedicated to uoa's. Now whether your motor will last 50 miles or 50k longer on a thicker oil who knows. When gm even says a thicker oil protects better people still don't listen. I'm surprised they even admitted that. Since they don't want your rolling computer on wheels to last. Well they want it to last just long enough to get you past the warranty then they want you to buy a new one.

Put whatever oil you want to in it. You're going to anyways.

 

[Antonm]

On 6.2L's with possible defective parts. Show me where it says that about 5.3's.

The bearings clearances specs are the same for all LT series engines (which are also the same as the previous LS series for that matter).

What will work and is good for one, will also work and be good for the other. The two engines are virtually identical save for bore size and tuning , they both even have the same crankshaft stroke (3.622 inches).

Ow20 oil is, and has been, working just fine in the 5.3, the thicker oil would just give a larger safety margin and is more tolerate to fuel dilution.

Is 0W40 oil "needed" in the 5.3 ,,,, nope it sure isn't. Would 0W40 oil help should the engine get a little to hot, or the oil change interval go a little to long, or a bunch of short trips causes excess fuel dilution in the oil, or with heavy towing/ extended high engine loading,,, yeap, it sure would.

But in reality, most of these SUV's are basic soccer mom mobiles and 0W20 will be just fine.

However , the only possible downside to running a 0W40 oil instead of an 0W20 is a slight (like very slight) reduction in fuel economy, nothing else. There is no circumstance at all, in any climate, under any condition, where an 0W20 oil will provide better engine protection than an 0W40 oil will. But in that same breath, but if you don't need that extra protection,,, then it doesn't really matter.

Think of it like keeping a printed road atlas in the car for road trips, most likely you won't need it, but there is also no downside to having it with you either, and should something go slightly wrong or abnormal (like you drop your phone and break it) it'd sure come in handy and might save your bacon.
...

 

[Z15]

The issue with the recalled 6.2L is traced back to supplier defects (crankshaft) and has no relationship to the oil viscosity. Millions of vehicles have been using 0W-20 since Circa 2010. I have used 0W-20 for 15 yrs in 4 GM trucks, never been any issue.

 

[viven44]

On 6.2L's with possible defective parts. Show me where it says that about 5.3's.

I agree with pretty much all of @Antonm 's explanation for LS engines.

Just want to recall that back in the day manufacturers would actually not spec only 1 viscosity, there were so many other factors such as driving condition, ambient temps.

Here is an approximation of engine oil temp based on thermodynamics of a system dissipating power (celcius is typically used but I'll use F here)

Engine oil temp (F) = ambient temp (F) + hp * thermal resistance of oil (F/hp)

Its simple, as the ambient temp increased, the engine oil temp increased linearly... obviously the engine oil temp in Texas is ~30-40F higher than in Alaska in Summer time. Once fully heated up, the oil is going to be thinner in Texas than Alaska, despite the engine working the same simply because of ambient conditions.

The following was pretty clear

There was a broadbased recommendation like the 5W-30 in the chart below but it wasn't the best or most ideal for the engine under all use conditions... this is all that we are talking about here (0W-20)

On the cold spec
-didn't change much unless you lived in an extreme cold climate... 10Ws would sort of head towards 5W.

On the hot spec
- Anything that had sustained operation in hot weathers would go from xW30 to xW40
- most if not all used xW30 on small blocks, and xW40 on big blocks. As the miles accrued, small blocks moved to xW40, and big blocks moved to xW50 before a rebuild was in order.

(Apparently straight 30 weight was better than a viscosity modified oil for the same rating)

Having all of this said, and getting back to the LS engines, I think it would be fair to say if you lived in Alaska/Canada/Northern states, you CAN stick to 0W-20 and do great. Down in Texas, I'd prefer something heavier like 5W-30. It is just better in the long run for the engine.

Also, if the truck is just a mall crawler or family hauler, by all means use 0W-20, but if it is actually being used as a truck, please just for the love of the engine, go up in viscosity as the power dissipation (in hp) is higher.