I don't know what Bo says but it looks like your data shows what us Amsoil dealers preach. Considering all of the variables, Amsoil 15W40 is a great value, probably the best value for your car. Also, for those readers with turbo cars, the synthetic are much better for your car than regular dino oils.
For more info on how Amsoil performs againts other oils in extended drain tests go to www.maxima.org
and click on the oil analysis spreadsheet in the general forums. I don't believe there are any diesel results there yet but there will be.