I have posted this once before. For clarification, I post here one more time.
Actually the "C" in CH-4 stands for "Commercial" and the "S" in SJ stands for "Service". It is a misconception when "C" is referred to as "Compression" and "S" as "Spark."
See publication by API at
BTW, I do not understand why the 15W-40 oil is not used widely in the US. Maybe the manufactures want to squeeze out that 1 MPG for CAFE standards. I have travelled to many countries and 15W-40 was the most widely used oil, truly a universal oil.
This past May, I travelled to China and there are so many taxi. Out of my curiosity, I asked what motor oil they use twice, once in Beijing (North) and once in Shanghai (South). Both time, the drivers showed me the 4-L jug they carry in the trunk. It is a Chinese made (Great Wall brand) 15-W40 oil. They say that is about the only oil all cars use in China. He further said the more expensive cars use import oils (I saw ads from Castrol, Mobile, etc) all over the place.
I saw this in the VW TDI board. Apparently BMW is seeing excessive engine wear with their newly recommended 5W-30 synthetic oil (regardless of drain interval) so many dealers are going back to BMW's 15-W40 premium oil. Other than being the messenger here, I do not know much more as I do not own a BMW. But at one time, I seriously considered to acquire the BMW synthetic oil to use in my MBs as the price is about $3.60/qt. A couple years ago, it was a 5W-40 synthetic made by Vavoline and about a year ago, they switched to 5W-30.