In the 1950's and 1960's, 'X-100' was used by Shell as the name of their premium engine oil - we had an add recently from Mycroft for this oil. I'm assuming the name went out of use sometime in the late 1960's, as in the 1970's through the 1980's Shell promoted their 'Fire and Ice' multigrades.
But, over in Thailand, Shell X-100 oil is still sold, it seems in straight 40 and 20W-50 viscosities, and is SF rated:
http://www.shell.com/home/content/thailand-en/shell_for_motorists/oils_lubricants/x100_0803.html
Interesting that a name that went out of fashion so long ago here is still used for that market. Wonder why that name survives, while other faded away....?
But, over in Thailand, Shell X-100 oil is still sold, it seems in straight 40 and 20W-50 viscosities, and is SF rated:
http://www.shell.com/home/content/thailand-en/shell_for_motorists/oils_lubricants/x100_0803.html
Interesting that a name that went out of fashion so long ago here is still used for that market. Wonder why that name survives, while other faded away....?