High-efficiency mechanism of enhancement of spreading performance of oil involving surfactant-laden oil droplet spreading over water surface

•Span 85, Span 80, Span 20, OP-4, and AOT greatly decreased the n-decane–water interfacial tension.•Span 85, Span 80, Span 20, OP-4, and AOT enhanced the spreading performance of n-decane droplets.•A system measuring the spreading performance of oil droplets containing surfactants on the air–water interface was built.•The law governing the spreading of surfactant-laden oil droplets on the surface of water has been systematically studied.•Surfactants in oil droplets migrated and were adsorbed at the oil–water interface, which was the mechanism of spreading.