SM vs. SM/SL

[vinu_neuro]

What does it mean when an oil specs SM compared to another which says it meets SM and also SL?

One example is Mobil 1 5W-40 compared to their other oils.

http://www.mobil.com/usa-english/motoroil/files/mobil_1_product_guide.pdf

 

[ahoier]

It's my understanding, if an oil meets "SM" it should also meet every spec that preceded (came before) it......?

Or am I wrong?

 

[flatlandtacoma]

You are correct.

 

[tomcat27]

every spec is backwards compatible - at least for the last 40 years...