Valvoline's atf+4 is labeled as "fully synthetic" Does this mean it's a group IV base oil? I'm wondering if i could get better performance/economy , and less shudder with a better atf+4 fluid. That is, a licensed fluid. Are there any comparisons available for different atf +4 brands? I find it incredibly difficult to believe that multi spec atf can do the job of atf+4.