Hydrotreated Vegetable Oil for Rail Applications: A Laboratory-to-Field Assessment of Fuel Performance, Compatibility, and Lubricant Condition

Hydrotreated vegetable oil (HVO) offers a renewable paraffinic alternative to conventional diesel, but its implementation requires assessment of fuel performance, component compatibility, and lubricant condition. This study combined laboratory investigations of non-additivated model blends with application-oriented testing of commercial, fully additivated B7 (diesel fuel containing 7 vol% fatty acid methyl ester) and HVO fuels and an industrial rail field trial. Model fuels containing conventional diesel, FAME (fatty acid methyl ester), and HVO exhibited nearly identical kinematic viscosities, whereas increasing HVO content improved low-temperature filterability, particularly at −20 °C. In accelerated oxidation tests, commercial HVO and B7 showed comparable oxidation induction times; however, HVO exhibited a substantially longer total oxidation time, lower chemical oxidation, and reduced deposit formation. Fresh HVO produced lower wear than fresh B7, while lifetime-aged fuels showed broadly comparable wear. Elastomer responses were material-dependent, with HVO generally causing lower mass uptake and less swelling. Two used-oil samples obtained after HVO passenger rail operation showed no indication of accelerated lubricant degradation or increased wear compared with B7 reference data. Overall, the results support HVO as a technically viable drop-in fuel for the investigated rail application, while highlighting the importance of fuel-specific compatibility and condition-monitoring assessments.