Let's be clear: API SL, SM, SN

[TechnoLoGs]

What are the DISTINCT differences and advantages of am API SL oil (starting) ten API SM (is still around,) and API SN (most current?)

How much "better" is an API SN oil than an API SL one? Or, can they be "worse?"

Trying to figure this out.. I thought API SN ushered in standards that made even the cheapest oils great, unlike API SL.. Hence, my confusion, as that may be totally wrong.

Discuss!

*And no, this isnt just for my car. ALL cars, ALL oils! API Sx...

 

[RamFan]

SL wasn't the first standard for starters. To compare them you should use the lubrizol comparison graph.

 

[d00df00d]

If you're looking at oils that meet the minimum standards for each, then SN is the best, followed by SM, and then SL. This is in terms of wear control and deposit control.

The thing is, most good oils go above and beyond the minimum, so you can't say just by looking at the API rating. It's possible for an extremely good SL oil to be better than a bare-minimum SN oil.

However, because you can't tell how good an oil is just by looking at the bottle, your best bet usually is still to go by the spec. Oils made to newer specs are more likely to have better base stocks and additive packages anyway.

 

[buster]

Use the Lubrizol spider chart.

 

[NateDN10]

As d00df00d said, each new spec increases the minimum standards the oil must meet. The reason people sometimes get their panties in a wad is that the newer standards also put a maximum Zn/P limits, to avoid poisoning catalytic converters (at least in xW-20 and xW-30 grades). This makes these oils less suitable for high-performance older motors with flat tappet cams.

But, looking at the standards themselves, SN >= SM >= SL in all areas.

 

[Danno]

Spider chart link.

http://www.lubrizol.com/EngineOilAdditives/ACEA/RelativePerformanceTool/default.html

 

[Ken2]

Techno, the differences are not great. They are real, and each new generation of oil is better than the last in some of the performance areas. It doesn't really matter what you use--use any top brand of the type and viscosity specified for your engine.

 

[d00df00d]

Originally Posted By: NateDN10
The reason people sometimes get their panties in a wad is that the newer standards also put a maximum Zn/P limits, to avoid poisoning catalytic converters (at least in xW-20 and xW-30 grades). This makes these oils less suitable for high-performance older motors with flat tappet cams.

Slight correction: API SM and SN actually have stricter wear control specs than SL does. So, even for flat tappets, SM or SN oils in xw-20 or xw-30 could still be okay.

Some people and manufacturers just want more ZDDP than API SM or SN will allow in an xw-20 or xw-30, which is why they look for API SL. But API SL alone doesn't guarantee more ZDDP. And either way, most of those people will be looking at xw-40 and up anyway, to which the low Zn/P limits don't apply.

Lastly, modern oil tech means you can use less ZDDP to do the same job or better. Newer forms of ZDDP work better, and there are all sorts of other ways to control wear these days without using ZDDP.

Whatever the case, the SM/SN flat tappet thing really isn't as much of an issue as it seems. As always, it's all about the overall formulation.

 

[JOD]

This is about as clear as it gets:

http://www.infineum.com/Documents/API/API Engine Oil Classifications 2010.pdf

with the caveat above being taken into account--these are minimum standards.

 

[danthaman1980]

To be clear; a modern, currently produced API SN should be superior in virtually every aspect to the API SL oils of 10-12 years ago.

However, as has been stated above, modern API SN and previous SM standards limit the Zn/P content in xW-20 adn xW-30 oils - which is why there some modern, currently produced API SL oils that contain more Zn/P (specifically talking about M1HM and Defy). These are superior to the 10-12 year old API SL oils. In all likelihood, they would meet current API SN if it weren't for the additional ZDDP.

For that reason, I do like the modern API SLs or other high-zinc alternatives for 2004 and older engines.

I'm not sure where GC stands on the spectrum since it was developed a while back and is still made in Germany. GC is a different animal.

 

[DemoFly]

From what I take away from this, is that I should really be looking for Dexos approved oil.

 

[Quattro Pete]

Originally Posted By: danthaman1980
I'm not sure where GC stands on the spectrum since it was developed a while back and is still made in Germany. GC is a different animal.

For an oil targeted at Euro cars/engines, the whole API SL/SN discussion is a moot point typically. For example, GC meets MB 229.5 spec. If one were to look at the lubrizol comparison tool linked above, MB 229.5 spec requirements outclass both API SL as well as SN in a number of performance categories by a long shot.

If I'm not mistaken, the OP started this thread because he was trying to find out which is better: SL-rated GC, or SN-rated M1 0w-40. He felt uneasy about GC because it was only SL-rated. However, both of these oils meet MB 229.5 spec, which to me makes them equally good, and both are way ahead of the API SL/SN requirements.