Gday,

Im hoping some one can clear up some of my confusion when it comes to the API oil grade alphabetical classification system. My question is this, as the ratings are all listed as S*, ie: SH or SJ etc, which ratings are better/higher on the rating system? Is SJ spec better then SH spec? or is SH spec better then SJ spec? From some quick research of done so far it seems to be that the closer the letter gets toward 'Z' the better the API grade. Can any one clear this up for me once and for all?

Cheers.

engine oil ratings appears as, eg: SF/CC the SF is the spec for spark ignition engines (petrol) and the CC is the rating for compression ignition engines (diesel). so the oils are SF/CC, SG/CD, SH/CE etc.
SF/CC grade oil was developed back in the early 60's, it made the 10'000km oil change interval possible. Revised oil specifications are released By the Society of Automotive Engineers (SAE) at about 10 year intervals to meet the demand created by tighter clearances and other changes in engine designs, and changes in emission laws in some parts of the world.
An oil of a newer specification even if it's the recomended Weight/Viscosity may not be suitable for an engine designed to run an older oil. But in my experience it usually has no negative impact. most of the SF/CC grade oil now sold in Australia is cheap recycled crap- I avoid it and run an SG/CD grade where SF/CC is recomended.

So basically, SL is better then SJ, ie: the closer the letter is to the end of the alphabet the better the API grade.