Preliminary results on nano-diamond and nano-graphite testing as additive for an engine lubrication oil

An important amount of the fuel energy burned in an internal combustion engine is used to overcome the friction losses inside the engine. Developing advanced lubricants is one of the ways to improve the fuel efficiency and reducing the pollution caused by internal combustion engines. This paper presents tests done with 1% v/v nano-diamond and nano-graphite additives in engine oils, with bench tests on an air-cooled spark ignition engine (Honda GX 160) with a displacement of 118 cubic centimeters. Using the raw lubrication oil laboratory, tests were done to determine the viscosity, density and viscosity index using an Anton Paar SVM 3000 viscometer in comparison to the oil with nano-diamond and nano-graphite additives. The tests also revealed an average reduction in fuel consumption of 21% for the single cylinder engine in case of the oil with additives, for the entire speed range of the engine, showing a decrease of the fuel efficiency as the speed increases. The temperature of the exhaust manifold, outer side of the cylinder and the temperature of the oil pan were measured. By adding nano-diamond and nano-graphite additives to the lubricant oil, tests have revealed a reduction of the temperature of the exhaust manifold (with 11%), temperature on the outer side of the cylinder was reduced with 21% showing a clear friction reduction within the cylinder and piston-rings assembly. The temperature of the oil pan was reduced with 20%, showing a general reduction of the lubricating oil temperature which means a substantial reduction of the friction losses.