The objective of this study was to obtain an improved understanding of the effects of the simultaneous use of cold flow improver (CFI) and antioxidant on the cold flow properties, oxidation stability and diesel exhaust emissions of various biodiesels and biodiesel blends. Cold flow properties were evaluated by assessing the cloud point (CP) and pour point (PP) values, as well as from the results of the cold soak filtration test (CSFT). Oxidation stability was also determined by measuring the peroxide induction period (IP). The neat biodiesels (B100) derived from soybean oil(SME), Jatropha curcus oil(JME), rice bran oil(RBME), palm oil(PME) and waste cooking oil(WME), and biodiesel blends with JIS No.2 diesel fuel were tested. A CFI and antioxidant specially designed for use in biodiesel fuels were employed during the work. The experimental data demonstrated that the addition of antioxidant had no effect on either the CP or PP values. The CSFT time value increases with increasing biodiesel content in biodiesel blends, although the addition of the CFI has little effect on the CSFT value. On the other hand, the CSFT results, however, were increased by antioxidant addition and also by increasing the CFI content in the SME(B100). The CSFT value was found to be well correlated with both CP and PP results in the case of the palm oil biodiesel. The IP value of SME(B100) is elevated with increasing CFI addition when an amine-based type antioxidant is added. We also determined that the addition of CFI and antioxidant reduces the extent of initial combustion due to premix combustion of DI diesel engines, which results in slightly decreased total unburned hydrocarbon (THC) and particulate matter (PM) emissions in exhaust at high engine loads.
