Abstract: A method of removing deposits in a direct injection spark ignition engine, the method including combusting in the engine a gasoline fuel composition having a quaternary ammonium salt additive wherein the quaternary ammonium salt additive includes the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; in which each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.

Abstract: A method of cleaning up internal diesel injector deposits in a severely fouled engine, the method including combusting in the engine a diesel fuel composition having (a) a quaternary ammonium salt additive; and (b) one or more further nitrogen-containing detergents; in which the quaternary ammonium salt additive includes the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; in which each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

Abstract: A method of removing deposits in a direct injection spark ignition engine, the method including combusting in the engine a gasoline fuel composition having a quaternary ammonium salt additive wherein the quaternary ammonium salt additive includes the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; in which each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

Abstract: A method of reducing the impact of deposits in a post combustion system of a diesel engine. The method comprises combusting in the engine a diesel fuel composition comprising as additives: (a) one or more quaternary ammonium salts; and (b) one or more compounds which are a product of a Mannich reaction between an (b1) aldehyde, (b2) an amine and (b3) an optionally substituted phenol. The method may be particularly effective when combusting a diesel fuel composition comprising renewable diesel.

Abstract: A method of cleaning up deposits in an indirect injection diesel engine, the method including combusting in the engine a diesel fuel composition having a quaternary ammonium salt additive; and optionally one or more further nitrogen-containing detergents; wherein the quaternary ammonium salt additive comprises the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; wherein each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

Abstract: A method of removing deposits in a direct injection spark ignition engine, the method including combusting in the engine a gasoline fuel composition having a quaternary ammonium salt additive wherein the quaternary ammonium salt additive includes the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; in which each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

Abstract: A method of cleaning up internal diesel injector deposits in a severely fouled engine, the method including combusting in the engine a diesel fuel composition having (a) a quaternary ammonium salt additive; and (b) one or more further nitrogen-containing detergents; in which the quaternary ammonium salt additive includes the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; in which each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

Abstract: A method of cleaning up deposits in an indirect injection diesel engine, the method including combusting in the engine a diesel fuel composition having a quaternary ammonium salt additive; and optionally one or more further nitrogen-containing detergents; wherein the quaternary ammonium salt additive comprises the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; wherein each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.