Influence of Copper oxide and Graphite additives on the lubrication performance of the engine oil

The parts of engine move at high speeds under heavy pressure. This leads to high temperatures and wear. To reduce the rate of wear, lubricants are used. But the lubricants are pollutants and increasing their useful life will result in the reduction of pollution. Additives may help in increasing the useful life of a lubricant. In the present study, the effect of the addition of cupric oxide and graphite nanoparticles to the engine oil on its performance of lubrication using pin on disc tribometer. AA2014 – 5 wt.% TiC composite material sliding against steel surface with lubricant was used to quantify the performance of additives. The base lubricant used in this study was 5W30 grade engine oil. Two types of lubricants, engine oil with 2 wt.% copper oxide (CuO) and engine oil with 2 wt.% Graphite (Gr) were tested and compared with the performance of the base oil in similar conditions. Adding Gr particles to the oil reduced the wear rate of sample by nearly 40% while CuO particles reduced the same by 43%. Similar trends were observed in friction coefficient too. The harder CuO particles may have pushed into the voids to create a compacted tribo layer which act as a coating to save the sample from wear. Although the addition of CuO particles improved the lubrication effect of the oil better than the Gr particles, the Gr particles have lower density and higher oxidative resistance, which makes them easier to mix and flow with the lubricant and remain stable without oxidation at high temperatures. The CuO particles are also harder and create craters on the surface when stuck between the contacting particles, this is confirmed by the scanning electron micrographs of the worn surface.