PURPOSE: To enable combustion in a cylinder of an engine to be promoted by an arrangement wherein the inner wall surface forming the combustion of the engine is coated with one or two or more than two kinds of metal oxide(s) selected from among Mn and other transition metals so that the combustion chamber may conduct a catalytic action and an adiabatic effect.

CONSTITUTION: The inner wall surface forming a combustion chamber 4 of an engine or the surface 3a of the combustion chamber of a cylinder head 3, the inner surface 6a of an air inlet valve 6 and the upper surface 2a of a piston 2 are coated with one or two or more than two kinds of metal oxides 8 selected from among transition metals such as Mn, Ni, Cu, Co, Cr, Fe and Zn etc. In this case, the above-mentioned metal oxide(s) 8 is/are formed by spray coating or enameling etc. This arrangement enables the metal oxide(s) 8 to conduct a catalytic effect and an adiabatic effect simultaneously so that the combustion of a fuel may be promoted by a simple and inexpensive construction.