This paper features an application study on the impact of different blend levels of commercially-supplied biodiesel on engine and aftertreatment systems' durability and reliability as well as the impact on owning and operating factors: service intervals and fuel economy. The study was conducted on a bus application with a 2007 on highway emissions equipped engine running biodiesel blends of B5, B20, and B99 for a total period approaching 4500 hours. Biodiesel of waste cooking grease feedstock was used for the majority of the testing, including B5 and B20 blends. Biodiesel of soybean feedstock was used for testing on B99 blend.
No negative impacts on engine and aftertreatment performance and durability or indication of future potential issues were found when using B5 and B20.
For B99 measurable impacts on engine and aftertreatment performance and owning and operating cost were observed. Fuel economy was negatively impacted by the reduced fuel energy content (expected result) and by high back pressure, caused by high ash levels generated from fuel that was out of specification. The high ash levels negatively impact the DPF ash service interval. Finally, the fuel injectors also showed signs of accelerated delivery loss attributed to the oxidation stability levels being near or below specification limits.
The B99 results further support the importance of validating that biodiesel fuel, at a minimum, meets ASTM D6751 standards before use. Even when B99 meets standards requirements, the results presented support fuel economy and ash service interval will still be negatively impacted, but to a lesser extent