MOTOR FUEL COMPOSITION COMPRISING A MIXTURE OF HYDROCARBONS IN THE GASOLINE BOILING RANGE CONTAINING (A) FROM 0.0004 TO 0.1 WEIGHT PERCENT BASED ON SAID COMPOSITION OF AN N-POLYAMINE SUBSTITUTED ALKENYL SUCCINAMIC ACID OR CORRESPONDING SUCCINIMIDE IN COMBINATION WITH (B) FROM 0.003 TO 0.20 VOLUME PERCENT OF (1) A POLYMER OF A C2 TO C6 UNSATURATED HYDROCARBON, (2) A COPOLYMER OF A C2 TO C6 UNSATURATED HYDROCARBON, OR (3) THE CORRESPONDING HYDROGENATED POLYMER OR COPOLYMER, SAID POLYMER OR COPOLYMER HAVING A MOLECULAR WEIGHT IN THE RANGE FROM ABOUT 500 TO 3500 AND A METHOD FOR OPERATING AN INTERNAL COMBUSTION GASOLINE ENGINE.