Today many global car makers are trying to improve Passenger Car’s Fuel Efficiency by the enforced CO2 regulation from a government, and there have often been global warming issues in decades. In 2010, the US Environmental Protection Agency (EPA) and National Highway Traffic Safety Administration (NHTSA) issued rules regulating the the greenhouse gas emissions and fuel efficiency of vehicles. These rules include the GHG credit benefit intended to provide sufficient lead time for manufacturers to make technological improvements and to reduce the overall cost of the program, without compromising overall environmental objectives. These credits allow manufacturers to have more effective transition to the increasingly stringent GHG standards and promote the innovative technologies that reduce vehicle CO2 emissions. The credits are earned through improvements to air conditioning systems that reduce refrigerant leakage or improve system efficiency(“Mobile Air Conditioning” credit) and implementation of technologies that reduce CO2 emission over driving conditions not captured by the standard test cycle used for compliance with the CO2 standards ( “Off-cycle” credit). Korea government announced the eco-innovation program to provide the credits for the innovative technologies that are not covered by the compliance standard test cycle. This paper is to analyze the background, requirements and procedures of MAC and Offcycle credits in US regulation for the reference of Korean eco-innovation program.