I know that the designation 'SE' and 'SD' on cans of oil used to stand for 'Small Engine' And 'Small Diesel' ........at least that's what I was told and never questioned it. But what do these stand for....."SG', 'SF', and 'SH'???????????????

 

http://api-ep.api.org/filelibrary/ACF1E1.pdf

this should tell you all you need.

 

Thanks Chris..........the link was exactly what I was looking for