The automaker is required to use language that strongly dissuades someone from using any oil grade that wasn't the one tested for fuel economy. I've posted EPA award letters here before and this type of intimidation must be used.Changed it to "imply warranty implications".
There must be 1000's of BITOG threads over the years where people start out by saying "I use xw-xx because they tell me too and I am scared to use anything else "
Its an implied threat. The auto industry makes billions off the milquetoast using fear tactics and implied threats. Perception is a real thing and a lot of people are afraid to go against the corporations. Just fact.
I could care less about CAFE anymore...we all know the numbers are manipulated by the automakers and the government knows this as well but as long as they can publish their report about how good we're doing...its wonderful. I wonder how many CAFE employees put thicker oil in their cars? Shirley they do because they know its a game.
It's not directly the manufacturers. They are doing what they are required to do.