isosyn, per my materials from the chevron conference, is a holistic means of combining optimized basestock and add packs to perfect performance. It does not really denote synthetic or any basestock with preference.
A major push was made to show the quality and value of isosyn and chevron products, particularly since texaco is being phased out. That said, the intent is to maintain havoline as the premium passenger motor oil product.
They made a big deal of delo being the premium product vs ursa for hdeo, but just made claims of the havoline as the premium product, no real backing data.