Abstract: Binary surfactant mixtures are added to particulate carbonaceous materials in oil slurries such as coal oil (COM) or coke oil mixtures in an amount sufficient to stabilize slurries during storage and dispersing at various temperatures. These stabilizer mixtures are added to either the oil or slurry and are effective with or without addition of water. Coal/coke oil slurries may contain from about 30 to about 90 parts by weight of oil, about 10 to about 70 parts by weight of powdered coal or coke, about 0.01 to about 6.0 parts by weight of the stabilizer mixture and about 0 to about 10 parts by weight of water. A useful stabilizer mixture contains from about 0.25 to about 0.75 parts by weight of an imidazoline quaternary salt and from about 0.75 to about 0.25 parts by weight of a nonionic surfactant which is ethylene diamine condensed first with about 80 moles of propylene oxide and then with about 20 moles of ethylene oxide.