Top Tier gasoline is gasoline that has added detergents for keeping the engine clean. It must meet certain industry standards. Your major, well- known gas stations like Chevron, Shell,76, Mobil will have gasoline in this category http://www.toptiergas.com/retailers.html
Happy, safe driving!
〉 Answered on Feb 11th, 2013 by Colleen McGee, Driving Instructor at Americas Driving School