Abstract
This study investigated the use of biodiesel (B100) and baseline diesel in two identical unmodified vehicles to realistically assess different aspects of biodiesel’s compatibility with modern common rail direct injection (CRDI) diesel engines and its effects on lubricating oil degradation and wear. Two identical vehicles were operated for 30,000 km each under identical operating conditions on highway during a field-trial while using biodiesel (B100) and baseline mineral diesel. Exhaustive experimental results from this series of tests were divided into four segments, and this paper covers the second segment showing the effect of long-term usage of biodiesel on the lubricating oil properties and traces of wear metal addition compared to baseline mineral diesel. Lubricating oil samples were drawn periodically from these vehicles for condition monitoring such as lubricating oil viscosity, density, soot content, total base number (TBN), ash content, trace metal concentrations, and thermal stability. The viscosity of lubricating oil samples drawn from biodiesel fueled vehicles were found to be ∼10–15% lower compared to that from diesel-fueled vehicles, whereas density and ash content were relatively lower by ∼5–10%. Carbon residues of lubricating oil samples drawn from B100 fueled vehicles were lower by ∼15–20% compared to that of diesel-fueled vehicles. There was a very strong reduction (∼70%) in the soot content of lubricating oil from biodiesel fueled vehicles. Trace metal analysis to compare wear debris addition was also done for all lubricating oil samples. Thermo-gravimetric analyses of lubricating oil samples from biodiesel fueled vehicles showed lower mass loss with increasing temperature hence relatively higher thermal stability and lower deterioration. Results also suggested that operational and durability issues associated with vegetable oils as alternate fuel were completely eliminated by using them after converting them into biodiesel meeting prevailing biodiesel specifications.
