Methods for producing fuel compositions with predetermined desirable properties are disclosed. Feedback control can be employed to meter precise amounts of fuel composition components while monitoring fuel composition properties to obtain fuel compositions having specifically defined properties.

A fuel additive composition, fuel composition, method of improving the injector performance of a fuel injected engine, method for preventing or cleaning up deposits in an engine or fuel system, method of reducing wear in a fuel system of an engine, and method of improving the demulsibility of a fuel composition. The fuel composition includes from about 5 to about 300 ppm by weight based on a total weight of the fuel composition of a hydrocarbyl soluble quaternary ammonium carboxylate derived from a quaternary ammonium carbonate and an organic acid.

The present technology is related to coupled quaternary ammonium salts, and the use of such coupled quaternary ammonium salts in fuel and oil compositions, or demulsification and/or engine performance of the compositions.

A method for treating an emulsion of a hydrocarbon is disclosed. The method includes providing an emulsion of a crude hydrocarbon, and adding an additive to the emulsion to obtain a treated hydrocarbon.