Abstract: A magnetic assembly adapted to be secured to a fuel line of a motor vehicle for improving the combustion of the fuel passing through the line by disposing the fuel line within a strong concentrated magnetic field without magnetizing portions of the engine proximate the assembly. The assembly comprises a housing, four primary magnets disposed within the housing and arranged in two adjacent columns of two magnets in each column with the south poles of each magnet facing toward the wall of the housing adapted to be disposed adjacent the fuel line, a plate disposed within the housing against the north poles of the two uppermost primary magnets in each column, and four secondary magnets disposed against the plate on the opposite side thereof from the primary magnets.