Then why the need for a "special" 6B category just for 0w16, why could it not fit into 6A?I've never thought it wasn't actually backward compatible (when of the appropriate grade for the vehicle).
or,
Why not 6A carry all the test specs of 6B and then just have 6A.
6B test specs are all of 6A's with some required improvements, etc, so why not just jam all the better stuff of 6B down onto 6A?