A discussion is presented on the various important features which need to be addressed in the design of viable thermal barrier coatings. The most economical way to ensure increased lifetime and operational safety of diesel engine components is to use a coating in order to improve surface properties. By comparing the surface material properties required for engine operations and the properties of coating systems achieved until now, it is evident that the fracture toughness must be improved. The activities include detailed characterization of powders, the coating microstructure and the properties required for engines. A correlation between in-service engine tests and model laboratory experiments will be discussed to the extent that the field test data are available.