What is the difference between SL, SM and SN Oils

[bigjl]

As per the title

What are the differences between SL, SM and SN.

Is it acceptable to use a SN when SM is specced? And is it ok to use SN when SL is specced? Or should you only substitute SL with SM?

Being familiar with ACEA specs I am just trying to get my head around the API specs.

Is there an API spec which relates to A3/B3/B4?

And also an API spec which relates to A1/B1, A5/B5?

 

[Falken]

Why my good chap, moving forward in designation by mantra shouldn't harm the previous spec in the application that it is replacing.

Oils now surpass spec's of two or three designations ago may also imply an adjustment upward in OCI length if a UOA is used.

 

[SR5]

The more modern API spec SN has tighter limits for things like deposit control (good) but it also has tighter limits on Zinc / Phos levels for xW-20 and xW-30 oils. This Zinc / Phos level is good for exhaust cats in an oil burner, but allows less ZDDP anti-wear adds, sort of win and lose. The older SL spec allows more zinc / Phos but also looser on other good specs like deposit control.

So if you want a 30 grade SL for zinc, then SN is probably a backward step. But if you want SL as a general oil quality measure, then SN is a step foward. So which is better is sort of context and application dependent. BTW just because SL allows more zinc, it doesn't mean it has more zinc, you have to look at the data sheets or a oil analysis (VOA).

The resource conserving A1/B1 and A5/B5 oils best correlate with the ILSAC GF-5 oils.

In Australia we get a Castrol Magnatec 5W-30 which is SN and A3/B4, so low Zinc but high HTHS.

We also get Castrol Edge 5W-30 which is SL and A3/B4 but also OEM MB 229.5, BMW LL01. So to get the higher quality OEM spec, they had to add extra ZDDP which dropped it from SN to SL, even though it meets all the SN quality requirements. This is a high Zinc and high HTHS oil.

Both the Magnatec and Edge are full synthetic Group 3 oils.

What I'm trying to point out is that there is not a direct and simple correlation between American API and Euro ACEA Ax/Bx. Both tell you something. In general I think ACEA set a higher bar than API.

 

[daves66nova]

Originally Posted By: Falken
Why my good chap, moving forward in designation by mantra shouldn't harm the previous spec in the application that it is replacing.

Oils now surpass spec's of two or three designations ago may also imply an adjustment upward in OCI length if a UOA is used.
I say, well put. Cheerio.

 

[wemay]

http://www.oilspecifications.org/articles/api-sn.php

 

[jorton]

I understand api revisions compliment manufacturers advances in engine technology. api sm oil would have benefited models that were technologically ahead of their time, like 90's Nissan VQ especially twin turbo engines.

 

[Garak]

Originally Posted By: bigjl
Is there an API spec which relates to A3/B3/B4?

That depends upon viscosity and, obviously, phosphorus content. An A3/B4 in 0w-30 or 5w-30 (and hypothetically 10w-30; we don't get a lot of 10w-30 A3/B4 options, as in none that I've seen) in North America tends to be SL or previous. If it's a 0w-40 or 5w-40 or other non-ILSAC grade, it tends to be SM or SN.

Originally Posted By: bigjl
And also an API spec which relates to A1/B1, A5/B5?

Those tend to be SN/GF-5 (or SM/GF-4 when that was current).

 

[CharlieBauer]

Originally Posted By: wemay

http://www.oilspecifications.org/articles/api-sn.php


That's quite impressive for 90 years and 12 revisions

 

[53' Stude]

Plus I believe SL oils had a higher allowance of phosphorus and other additives and SM oils were "energy conserving"

SN oils are "resource conserving"

 

[A_Harman]

SL oils had a maximum Phosphorous content of 1000 ppm in the 20 and 30 grades.
SM lowered max Phos to 800 ppm for 20 and 30.
SN added requirements for ZDDP volatility, so that more of it stays in the engine and out of the catalytic converter.
I think SN is altogether an advancement on SM, as shown in the spider diagram above.
You can still get higher ZDDP in SN oils; just buy a light 40-weight, such as Castrol or Mobil 0w40. They're just barely into the 40 range.

 

[supercity]

Originally Posted By: bigjl

Is there an API spec which relates to A3/B3/B4?

And also an API spec which relates to A1/B1, A5/B5?


API SN, SM etc are petrol specs only
ACEA (PCMO) specs are all petrol and diesel specs

All ACEA specs (A/B, C) can potentially meet SN or older API categories
SN formulations may not meet any ACEA spec.

So there is no matching an ACEA (PCMO) to an API spec alone.