Formula didn't change. The label did... Which doesn't make a lot of sense, but someone here did some digging and found that out for us. Mine ran fine with Mobil 1 through two changes before I switched to Amsoil due to the label/rating change on the Mobil 1.
If i remember correctly?? Lamont posted that his clutch started slipping after using Mobil 1:dontknow:
It was in an old post, I think those are lost now?