Synthetic two-stroke engine oil as a tool of exhaust emission control

Polypropylene oligomers were used to formulate two-stroke (2T) engine oil for once-through lubrication systems, to enhance the exhaust emission characteristics of two-stroke engines. The oligomers alone are suitable from a stability viewpoint, but must be reinforced with polyol-ester components to have good load-carrying capability. Both ash-forming and ash-free commercial additive packages can be used to formulate the end-product. The exhaust stream includes the unburnt portion of the fuel:oil mixture. The lubricating oils formulated on polypropylene oligomer base do not contain polynuclear aromatics, the sulphur-dioxide emission is due to the sulphur content of the fuel and additive (if any). On a bench test, the hydrocarbon emission was significantly lower using polypropylene oil, in comparison to using a commercial mineral-oil-based composition.