Why do automakers disaprove?

[Mark72]

API’s Lubricants Committee approved the SN and SN Resource Conserving passenger car engine oil categories, with first licensing Oct. 1, 2010, launching alongside ILSAC GF-5. The thumbs-up came in spite of continued opposition from automakers

 

[kevinf]

As I understand it, they like the GF-5 standard which is the same as the "SN Resource Conserving". They don't like the plain old SN certification because it will confuse consumers as the automakers are going to insist on "SN Resource Conserving"(GF-5) during the warranty period for new vehicles.