SAE J300 Viscosity Grades

When you buy a quantity of oil, probably the first thing you look for is the SAE grade. But what do these numbers represent; what do they mean? In this post we will explore the fundamentals of SAE J300, which is the standard under which these grades are defined and often a point of considerable confusion.

At its simplest, a multigrade oil is identified by two numbers:
1. The Winter grade, this is the number BEFORE the W
2. The SAE grade, this is the number AFTER the W

These numbers are not related.

Both numbers (grades) represent clearly defined ranges, outlined as follows:

Winter Grade
The Winter grade is determined by the oil's ability to meet the performance requirements of two tests:
1. CCS - Cold Cranking Simulator - This is designed to simulate the impact on the speed at which the engine can be turned over by the starter
2. MRV - Mini Rotary Viscometer - This is designed to simulate the oil's ability to make its way up the pick-up tube and be pumped

The limits for CCS are much lower than for MRV, so it is typically CCS that the oil fails, which then determines the Winter grade of the lubricant. So, for example, if an oil tested at 6,200cP at -30C, looking at SAE J300, we know it would not meet the performance requirements of the 0W-xx Winter designation, but we can see that it's below the limit of 6,600cP for the 5W-xx Winter designation, so the oil would be labelled as a 5W-xx.

*Multigrade oils are required to be labelled with the lowest Winter grade they meet* This means that an oil that meets the requirements for the 5W-xx designation cannot be labelled as a 10W-xx for example.

SAE Grade
The SAE grade is determined by the oil's viscosity at 100C and its HTHS viscosity at 150C. HTHS is only really a factor in grades where there is overlap, like 8, 12, 16 and 20.


SAE J300 from the Afton Specification Handbook:

When mixing oils of different viscosities together, you can use a viscosity calculator like the one provided by Widman:

https://www.widman.biz/English/Calculators/Mixtures.html​

to determine the SAE grade.

So, for example, if we mixed equal parts of a 5W-20 with a KV100 of 8.6cSt with a 5W-40 with a KV100 of 15.2cSt, we get a KV100 of 11.34cSt, which, looking at J300, puts us right in the middle of the range for the SAE 30 grade.

But what about the Winter grade? That's more complicated, and cannot be calculated in the same manner. While the odds are, with both examples carrying the 5W-xx Winter grade, that the resultant mix is an SAE 5W-30, we cannot know that for sure. Different VII's, base oils and PPD's behave differently together and it's possible that it may not pass the 5W-xx Winter grade CCS and MRV testing.

Anomalies in the Winter grade are more likely with wider spreads, where one of the constituents of the mix is using a considerably heavier base oil, like say a 20W-50. So, for example, if you mixed a 0W-30 with a 20W-50, one might expect a 10W-40, but it may in fact be a 15W-40 or possibly even a 20W-40 (though unlikely), depending on how close to the 20W limit the 20W-50 was in the first place. Wax crystal formation, which is what drives the rapid increase in viscosity below freezing in non-PAO base oils, tempered by PPD's (Pour Point Depressants), is unpredictable in these mixing scenarios because the dose in each constituent is based on the blend for that specific product and a 4cSt GTL base oil for example, is going to require a different PPD dose than an 8cSt Group II.

 

[4WD]

Not what I was referring to

Read above w30 when meaning SAE 30

What a bunch of semantics - heading outside to 60°

 

[RDY4WAR]

I think the term "weight" either stems from, or is the cause of, the "W" in a multi-grade being misunderstood to mean weight. This in turn has caused people to think the first number of the multi-grade is the actual "weight" resulting in misinformation surrounding the grades and what they mean. This is why I don't like it. It's almost a daily occurrence on social media where I see someone suggest using a 10W-30 instead of a 5W-30 because it's thicker, and to not use a 0W-xx because it's like water. They firmly believe a 5W-50 is lower viscosity than a 10W-30 because of this misunderstanding.

Just yesterday, someone vehemently recommended a person use conventional Castrol GTX 10W-30 because the Mobil 1 FS Euro 0W-40 was "way too thin". The application called for MB 229.5.

 

[MolaKule]

I think the term "weight" either stems from, or is the cause of, the "W" in a multi-grade being misunderstood to mean weight. This in turn has caused people to think the first number of the multi-grade is the actual "weight" resulting in misinformation surrounding the grades and what they mean. This is why I don't like it. It's almost a daily occurrence on social media where I see someone suggest using a 10W-30 instead of a 5W-30 because it's thicker, and to not use a 0W-xx because it's like water. They firmly believe a 5W-50 is lower viscosity than a 10W-30 because of this misunderstanding.

Just yesterday, someone vehemently recommended a person use conventional Castrol GTX 10W-30 because the Mobil 1 FS Euro 0W-40 was "way too thin". The application called for MB 229.5.

And this was the original theme and reason for establishing BITOG; to educate!

 

[FlyingTexan]

Not what I was referring to

Read above w30 when meaning SAE 30

you know what i meant which wasd the exact point, Would Xw30 or Xw40 or Xw-30 or Xw-40 make everyone feel better? i'm still not doin it. i'm on a flight typing one handed on my way back from nigeria because theres someone in the middle seat next to me and no room. i guess if it's too much for someone to grasp then its too much. done with that topic

 

[ZeeOSix]

I understand that it’s just a common way to not say 30 or 40 or weight

The better way to do it would be xW-30 or xW-40. If someone can type a 150+ character post, they should be able to add an x to the mix.

 

[Pablo]

The better way to do it would be xW-30 or xW-40. If someone can type a 150+ character post, they should be able to add an x to the mix.

Or just write SAE 40 or SAE 40 viscosity range

 

[ZeeOSix]

Or just write SAE 40 or SAE 40 viscosity range

That would be OK if it wasn't a multi-viscosity grade.

 

[kschachn]

That would be OK if it wasn't a multi-viscosity grade.

It would be. It's not as if the SAE is clueless on this issue.

 

[Pablo]

That would be OK if it wasn't a multi-viscosity grade.

Sure but our language is vis at 100°C. Like it or not.

 

[ZeeOSix]

Sure but our language is vis at 100°C. Like it or not.

True ... if someone writes "SAE 30" it technically means it's not a multi-viscosity grade oil, but the "30" is still the KV100 SAE grade.

 

[kschachn]

True ... if someone writes "SAE 30" it technically means it's not a multi-viscosity grade oil, but the "30" is still the KV100 SAE grade.

The only exception under SAE labeling rules would be if it as an monograde also qualified for a multigrade designation, but the blender decided not to include that on the label. But it would still also be a monograde at the same time. It couldn’t have any VM of course.

 

[ZeeOSix]

The only exception under SAE labeling rules would be if it as an monograde also qualified for a multigrade designation, but the blender decided not to include that on the label. But it would still also be a monograde at the same time. It couldn’t have any VM of course.

Yes, every oil could be labeled as a "multi-grade", dependent on what W grade it falls into and what KV100 grade it falls into per SAE J300. For instance, HPL sells multi-grade oils that have no VMs/VIIs. If an oil is labeled as "SAE xW-yy" then it's sold as a multi-grade oil. If it's labeled as "SAE xx", then it's sold as a straight weight oil.

 

[kschachn]

Yes, every oil could be labeled as a "multi-grade", dependent on what W grade it falls into and what KV100 grade it falls into per SAE J300. For instance, HPL sells multi-grade oils that have no VMs/VIIs. If an oil is labeled as "SAE xW-yy" then it's sold as a multi-grade oil. If it's labeled as "SAE xx", then it's sold as a straight weight oil.

Every oil that meets the requirements for an SAE multigrade yes. But some monogrades would not.

 

[ZeeOSix]

Every oil that meets the requirements for an SAE multigrade yes. But some monogrades would not.

I'd bet most (not all) oils labeled as a single grade "SAE xx" would fall into an SAE J300 W grade and an SAE J300 KV100 and HTHS grade, and could be labeled as a multi-grade, but you might get some pretty weird multi-grade ratings that would just confuse people and obviously not meet OM viscosity call outs.

 

[Overfill]

Question for labeling.

I understand that to be labeled as a monograde, the oil must not contain any VII/VM, but it could be sold as a multigrade as long as it tests and passes under such labeling. Does the absence of VII/VM also allow it to be marketed and sold at winter grades above what it can test at?

eg: synthetic SAE 20 (VII/VM-free) that performs as 0w-20.
Can this be sold as
5w-20
10w-20
15w-20
20w-20
25w-20
or is the seller still constrained under multigrade labeling to display the lowest winter grade it would perform to?

 

[OVERKILL]

Question for labeling.

I understand that to be labeled as a monograde, the oil must not contain any VII/VM, but it could be sold as a multigrade as long as it tests and passes under such labeling. Does the absence of VII/VM also allow it to be marketed and sold at winter grades above what it can test at?

eg: synthetic SAE 20 (VII/VM-free) that performs as 0w-20.
Can this be sold as
5w-20
10w-20
15w-20
20w-20
25w-20
or is the seller still constrained under multigrade labeling to display the lowest winter grade it would perform to?

My read on the regulation is that it has to be labelled as the lowest Winter grade it meets, if it is going to be carrying a Winter grade designation. So if it performs like a 0W-xx then that's what it needs to be labelled as (if it's going to carry the Winter grade).

 

[Blang]

Question.... how can something be a 'multigrade' oil if there's literally only one designation for the SAE grade? The number before the W is the 'Winter' rating, not the SAE grade right?

 

[OVERKILL]

Question.... how can something be a 'multigrade' oil if there's literally only one designation for the SAE grade? The number before the W is the 'Winter' rating, not the SAE grade right?

It's the Winter grade, as noted in the OP.

 

[lakestone]

And this was the original theme and reason for establishing BITOG; to educate!

Wow, who started it?

 

[MolaKule]

Bob.