Publisher Summary Waste engine oil, essentially composed of hydrocarbons, is an excellent fuel; furthermore, it does not contain a heavy residual fraction characteristic of heavy fuels. This characteristic explains why the fuel gas produced by oil combustion does not contain unburned solid carbon particles called cenospheres. Important restrictions are imposed on the combustion of waste oil classified as hazardous waste. This means that energy recovery is and will be, in most cases, subject to additional costs of effluent gas treatment. The need to satisfy the emission limit values for this waste seriously limits its application. As well as the advantages, the oil can contain polluting solvents that must be eliminated. Metallic and metalloid compounds must also be eliminated, since they are transformed into oxides carried by the combustion gas and partially transformed into sulfates that are then deposited in the combustion chamber.