Thick ceramic coating by plasma-jet spraying represents a novel and essential engineering tool which enables many products to be manufactured economically. A 1 mm thick alumina (A12O3) coating on an automobile piston was produced by plasma-jet spraying, thus surpassing the former thick alumina layer of 0.3-0.5 mm. This thick ceramic coating can be applied to automobile pistons by the new plasma-jet technology. Such coatings are practical and useful for increasing wear-resistance, heat-resistance and corrosion-resistance. Reduced fuel consumption from 245 to 225 g/PShr and improved thermal efficiency, from 20 to 21 % compared with uncoated pistons, were obtained.