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Recently, Gasoline Direct Injection (GDI) engine has reached mass production. Fuel economy up to 35% is claimed, at urban driving conditions, by using stratified charge combustion. It also reduces HC emissions at cold start. Most of the car manufactures are researching GDI or even intend to produce it in the near future. If the promised goals are actually achieved, a great change in the development focus for automotive engines will occur. In GDI engines, ultra lean burn, stratified charge combustion is achieved by injecting fuel directly into the chamber during compression stroke (“late Injection”). In contrast, at higher power conditions, the GDI operates in homogeneous charge and fuel is injected during intake stroke (“early injection”). This paper intends to summarize some information about Gasoline Direct Injection engines and possible effects on Piston rings. First, some basic concepts about combustion, judged to be necessary to understand GDI engines, are introduced.