Thanks for the link to that article. Wish I can find Shell around here.
Sponsors of the Top Tier rating make no claim that such gasolines will clean dirty engines, only that they will keep clean engines clean.
Automakers that sponsor the Top Tier rating system: Audi, BMW, General Motors, Honda, Toyota, Volkswagen.
More on Top Tier: www.toptiergas.com/
U.S. Top Tier brands (listed alphabetically)
Aloha Petroleum (sold in Hawaii)
Entec (mainly sold in Alabama)
Kwik Trip (mainly sold in Minnesota, Wisconsin)
MFA Oil (sold at Break Time convenience stores)
Somerset Oil (mainly sold in Kentucky)
Tri-Par Oil (mainly sold in Wisconsin)