Base Oil Viscosity Discussion Thread

[TallPaul]

I moved this from the "10 cSt difference" thread since it was hijacking that thread and warranted it's own discussion. Also moved all the discussion here, sorry didn't give all credit where due, was difficult. Probably should have asked G-man to move this for me, but anyway here it is:

The October Lubes 'n' Greases (Page 8) has a table giving typical base oil 100C viscosities for base oils used in making finished oils:

5w20 is 3.9 cSt
5w30 is 4.1 cSt
10w30 is 6.0 cSt
SAE 30 is 9.3 cSt
10w40 is 5.5 cSt
15w40 is 7.0 cSt
and 20w50 is 10.2 cSt

I would assume the additive package brings the SAE 30 up from the listed 9.3 cSt to a typical 10.5 cSt.

 

[TallPaul]

Bruce quoted and responded:

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I would assume the additive package brings the SAE 30 up from the listed 9.3 cSt to a typical 10.5 cSt.

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Yes

 

[TallPaul]

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Holy Smokes!

You mean that's the viscosity of the oils before Viscosity Index Improvers are added?!?

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Yes, and also before additive package is added. And now I see another area where (all else equal) 10w30 is superior to 5w30 for all but extreme cold.

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[TallPaul]

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Yes, and also before additive package is added.

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Does that mean the additives increase the viscosity too?

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Yes. The standard PCMO additive package Bruce kindly gave me to play with is 65 cSt at 100C (and has 21000 ppm zinc etc.). For 5 qts of SA rated oil (pretty much base oil with no additives) it would take maybe 8 or 10 ounces of the PCMO additive to make the SA into a SL with about 1000 ppm zinc. So that 8 to 10 oz of 65 cSt will jack up the base oil viscosity.

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[TallPaul]

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Of interest in the SAE30 discussion is that the October Lubes 'n' Greases (Page 8) has a table giving typical base oil 100C viscosities for base oils used in making finished oils:

5w20 is 3.9 cSt
5w30 is 4.1 cSt
10w30 is 6.0 cSt
SAE 30 is 9.3 cSt
10w40 is 5.5 cSt
15w40 is 7.0 cSt
and 20w50 is 10.2 cSt

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And I suspect SAE 20 starts with a base oil of around 7.5 cSt.

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[TallPaul]

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10w30 is 6.0 cSt
10w40 is 5.5 cSt

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So 10w40 starts out with a lighter base oil than does 10w30...???

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Well it's either a mistake or it has to be lower to meet the 10w requirements in combination with the much greater amount of VII required for a 40 weight.

 

[Pablo]

I can't seem to find my Oct issue (did it come yet?)

Anyhow - yes in general those may be the starting base oils for VII enhanced PCMO, but remember there are more than two paths to get there. Mixes of base oils are popular.

 

[TallPaul]

Yeah, the chart is generalized and in fact from older data, but they say it still is representative of current mixes. The reason you can't find the October issue is that this time I signed up for electronic magazine and the link was emailed to me yesterday.

 

[TallPaul]

Pablo, your PM box is constipated. Check your regular Email.

 

[Pablo]

Unconstipated. Always full..........dang....I just deleted 300+ the other day. Thanks - got the link.

What's with all the bruce chat and no bruce?

 

[TallPaul]

I was having trouble copying all these posts. Bruce only posted the one item above (in the other thread). Other posters were Merkave 4 (next two posts) then G-man on the SAE20. The 10w40 question was posted by Camu Muhabah. It all came from this thread.

 

[Max_Wander]

This is info I was pondering the other day, "are engine oils started with a thin base with VIIs added or are they corresponding straight grades with PPDs installed?" Now I have my answer!

 

[Master ACiD]

i would feel better running an oil that started with a thicker base. that 30 looks good, but i have 50 some odd gallons of 15w40 i got for free. that 15w40 base oil thickness also seems good. alot better than the 5w20!

5w20 is 3.9cst. the number 2 diesel i buy from my local jobber has a viscosity of 2.52 at 40c. tyhat means that at a lower temp, say 15 degrees, diesel fuel would be as thick as 5w20 at 100 degrees.

maybe the quote in my signature isnt too far off! hahaha.

 

[Gary Allan]

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the number 2 diesel i buy from my local jobber has a viscosity of 2.52 at 40c. tyhat means that at a lower temp, say 15 degrees, diesel fuel would be as thick as 5w20 at 100 degrees.

maybe the quote in my signature isnt too far off! hahaha.

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"Kerosene that is fully additive formulated may make a good oil." -aehaas

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Bruce and I chuckled at your sig in one of our exchanges about Bruceblend®. He said it's not too far off of the mark.

 

[JAG]

What I found interesting is that the current M1 0W-40 is less volatile than Green and Gold GC. Both GCs have nearly identical volatility. American Castrol Syntec 5W-40 is more volatile than GC. When you put really high-tech synthetic basestocks on the table, much is possible. I pointed these examples out because they break some general trends due to the wide range of basestocks used in them.

 

[Merkava_4]

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10w30 is 6.0 cSt
10w40 is 5.5 cSt

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So 10w40 starts out with a lighter base oil than does 10w30...???

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Well it's either a mistake or it has to be lower to meet the 10w requirements in combination with the much greater amount of VII required for a 40 weight.

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I'm thinking the numbers are correct. I'm thinking 10W-40 needs the thinner base oil with the loaded up VII's to give it the needed stretch for its wide viscosity range. And since 10W-30 doesn't have to stretch as far, it can have a thicker base oil.

 

[G-MAN]

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10w30 is 6.0 cSt
10w40 is 5.5 cSt

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So 10w40 starts out with a lighter base oil than does 10w30...???

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Well it's either a mistake or it has to be lower to meet the 10w requirements in combination with the much greater amount of VII required for a 40 weight.

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I'm thinking the numbers are correct. I'm thinking 10W-40 needs the thinner base oil with the loaded up VII's to give it the needed stretch for its wide viscosity range. And since 10W-30 doesn't have to stretch as far, it can have a thicker base oil.

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VI improver is going to thicken the oil at all temps just by virtue of its extremely high vis (some are even solid). Thus, with more VII (as would be needed for a 10w40) the thicker the oil is going to be at low temps. So to meet the CCV requirements for a 10W, the 10w40 has to start with a thinner base oil blend.

 

[Drivebelt]

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5w20 is 3.9 cSt
5w30 is 4.1 cSt
10w30 is 6.0 cSt
SAE 30 is 9.3 cSt
10w40 is 5.5 cSt
15w40 is 7.0 cSt
and 20w50 is 10.2 cSt

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Those 5W numbers don't seem correct.

If you look at Chevron's base oil page, they have a table where it states that a 5w-20/5W-30 (GF-4) can be blended with 5R and 220R …

5R ……4.7 cSt
220R …6.4

Given the viscosity of those 2 base oils, there is no way to blend the base oils lower than 4.7 cSt (100% 5R = 4.7) -- so I don’t see how the 5W's can be around 4.0 cSt.

FWIW … when I researched the issue of base oil use in motor oils a few months ago, although it was pretty hard to come up with some concrete numbers, I arrived at the following …

5W-20 … 4.9 cSt
5W-30 … 5.1 cSt
10W-30 … 5.6 - 5.8 cSt
15W-40 …~ 7.0 cSt

These would be for Group II base oils. If blending with Group III or PAO, the viscosity of the base oils would be higher because they have better cold flow properties.

 

[G-MAN]

I would suspect the numbers given in that article reflect Group I usage. If Group II is used you could get away with a thicker base oil blend because of the higher VI of Group II. And if PAO and esters are used, you could go even thicker.

 

[Merkava_4]

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If blending with Group III or PAO, the viscosity of the base oils would be higher because they have better cold flow properties.

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That explains why Synpower 5W-40 pours down the funnel faster than Maxlife 10W-30.