Any 5w20 that meets Ford's spec (which requires a double length Sequence IIIF test) will have to have some Group III in it. Johnny has posted that Pennzoil's 5w20 is 40% Group III. Since most 100% synthetic oils sold at retail are Group III based, companies could call their 5w20s a "synthetic blend" if they label their Group III oils "full synthetic." Most choose not to, however.