Then, it will be buried in a soil for a set number of days in biodegradation process. The result shows that the biodiesel oil has the most toxic during the treatments. Soyabean oil also has toxicity during the treatments, but at a very slow rate. The rate of toxicity of both soyabean oil and biodiesel oil can be seen from figure 2.2. Toxicity in biodiesel oil is higher in comparison to the soyabean oil because the biodiesel oil has a formation of the secondary compound during the biodegradation, which is third-butyl hydroquinone (TBHQ). The secondary compound from the biodiesel is the reason for an increase in toxicity (Tamada et al., 2012). In conclusion, the amount of toxicity in soyabean oil is lower in comparison to biodiesel that is produced from mineral-based oil (mostly non-biodegradable). Thus, the use of vegetable oils as lubricant is favourable because it is biodegradable and …show more content…
One of the criteria that need to be met is to have a relatively high viscosity index (Ştefănescu et al., 2005; Wikipedia, 2016b). Viscosity is defined as a measure of a resistance against its flow, which can be measured by numerous of methods while the viscosity index is a measure of changes in viscosity with temperature. Few articles have noted out the importance of viscosity index in a lubricant. Fitch (2012) mentioned it is too often the viscosity index is disregarded as a lubricant selection parameter as it is very important. The viscosity index of lubricants is very important to acknowledge as viscosity provides the film thickness and film strength in machines process. Moreover, viscosity index also influences many factors in lubrication such as wear rate, lubricant life expectancy, energy consumption and fluidity. Therefore, it is advantageous to know the viscosity index of a solution so that these factors would not affect the performance of a