BULLETIN ! : SG is now an obsolete rating. Current ones are SJ/SL/SM/SN
Go to the American Petroleum Institute site and get the ratings guide, use the current standard, and stop stressing over oil ratings. For those still worrying about thin oil and what temperatures are used with what viscosity rating, the bottom of the last page in the PDF file noted below shows the temperature ranges recommendations. PDF file is here:
http://www.api.org/certifications/en...010_120210.pdf
Now go ride and quit wasting bandwidth, time and oxygen worrying about oil.
