Combustion chamber deposits accumulate in a new gasoline engine and can result in an octane requirement increase (ORI) of as much as 8 to 10 octane numbers. In some cases, a higher octane fuel is required to prevent engine knock (detonation).A unique new additive concentrate has been developed which reduces combustion chamber deposits and lowers the engine's octane requirement. This new additive is an ashless dispersant based on polyether amine chemistry. Laboratory and fleet test results show that after using one tankful of gasoline treated with additive, the engine's octane requirement is typically reduced by 30% to 40% of the original engine ORI. This benefit lasts for several thousand kilometers until the deposits reestablish themselves in the combustion chamber.In addition to the octane requirement decrease (ORD) effect, other benefits from the use of this additive include engine run-on reduction and intake system deposit cleanup.