Impact of Biodiesel Blends on Fuel System Component Durability

An ultra-low sulfur diesel (ULSD) fuel was blended with three different biodiesel samples at 5 and 20 volume percent. The biodiesel fuels were derived from rapeseed and soybean oils, and in addition, a highly oxidized biodiesel was prepared from the soy biodiesel by oxidation under controlled conditions. A set of five elastomers commonly used in automotive fuel systems were examined before and after immersion in the six test blends and base fuel at 60°C for 1000 hours. The elastomers were evaluated for hardness, tensile strength, volume change and compression. Injector wear tests were also conducted on the base petrodiesel fuel and the biodiesel blends using a 500-hour test method developed for this study. Bosch VE (in-line) rotary pumps were evaluated for wear after testing for 500 hours on the base fuel, B5 and B20 test fuels. Additionally, a test procedure was developed to accelerate wear on common rail pumps over 500 hours. This procedure was used to evaluate Bosch pumps from tests conducted on the base fuel, B5, and B20 fuels. B5 blends, even with highly oxidized biodiesel, appeared compatible with the materials and components tested. B20 blends from non-oxidized biodiesel also appeared to be compatible with these materials and components. Test results for B20 prepared from highly oxidized biodiesel suggest the potential for significant problems with oxidized fuels, highlighting the need to prevent biodiesel oxidation. However, due to a lack of real-world field oxidized biodiesel samples for comparison, verifying the severity of the oxidization level of the biodiesel used in this study is not possible. There is some potential that the highly oxidized biodiesel sample used in the study represents an extreme condition that consumers may not encounter in the field; therefore, additional work is needed.