Thermal barrier coatings (TBCs) have been employed for ten years in all types of diesel engines. TBCs have been used to reduce corrosion of pistons and valves, improve fuel efficiency, reduce pollution, allow use of lower quality fuels, improve cost start capability, reduce maintenance costs, improve power and improve lube oil life. Recently much interest has been demonstrated by transit operators in TBCs for pollution control and fuel economy results. A summary of the experience to date, current bus-related activities and advancements in thermal barrier coatings will be discussed.Diesel TBCs (thermal barrier coatings) are plasma-applied ceramic coatings which insulate combustion components such as pistons, valves and fire decks from thermal transmission and shock. Similar coatings have been effectively used in the aerospace industry for many decades. The developer of GPX Diesel-4 Ceramic Coatings, General Plasma of East Windsor, Connecticut, and the diesel distributor, FCS Inc. of Centerbrook, Connecticut, have reported some major successes in emissions reduction and improved engine performance with the use of diesel TBCs. A 10-year study conducted by FCS on the benefits of ceramic thermal barrier coatings in diesel applications was the driving force behind the development of the new GPX coating line.