Lube-Tech
bearings in the early 2000s, the practice of utilising zinc-free oil has continued to protect the existing fleet that contains these silver bearings and remains prevalent in the industry today. Prominent additive companies such as Oronite and Infineum continue to cater to the demand for zinc-free engine oils within the industry [7].
In general, additives are added to engine oil formulations to enhance the base fluid and ensure that the finished product meets certain specifications and performance baselines outlined by the manufacturers and environmental regulators. The Locomotive Maintenance Officers Association (LMOA)’s Generation 7 engine oil specification has been established to comply with EPA emissions regulations for Tier 4 (Gallagher, et al., 2016).
The selection of locomotive engine oils depends on a series of factors, one of which includes the sulphur content in the fuel. Given the current global fuel inventory utilised in the rail industry, oils with a Base Number (BN) ranging from 9 to 13 are used to effectively neutralise sulphuric and other acidic by-products produced during the combustion process. In North America, Generation 7 oils with an 11 BN, as determined by ASTM D2896, are considered the standard. Other countries have employed the use of Generation 7, 6, and 5 (or 4LL) oils depending on available fuel and engine type. Compared to Generation 6 oils, Generation 7 oils demonstrate improved base retention and acid control. They are better equipped to handle the added demands posed by the Exhaust Gas Recirculation (EGR) systems and reduced oil consumption in GEVO Tier 4 engines. Furthermore, they maintain compatibility with low (<500 ppm) and ultra-low (<15 ppm) sulphur fuels [8]. As emissions regulations potentially become more stringent and as new formulations offering greater performance gains are developed, the pursuit of such enhancements is expected to continue in future locomotive engine oil formulations.
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.148 page 3
For the past few years, the use of synthetic engine oils instead of conventional (mineral) oils has become more popular in the automotive industry due to their improved performance and potentially extended oil drain intervals. A similar potential exists within the railway industry. However, the railway industry may find similar levels of application too expensive for older locomotives that may consume more engine oil and newer locomotives since oil contamination will and getting to recommended condemning limits triggers an immediate oil change. Some of these locomotives that are built with older-generation diesel engines have extremely high oil consumption in comparison to a typical car or truck. This makes the use of synthetic oil cost prohibitive. Nonetheless, it may prove useful to utilise synthetic oils in newer locomotives, which could potentially enable longer ODI, increase fuel economy, and improve durability [9].
The automotive industry is witnessing a notable shift towards lower viscosity engine oils. The presence of 15W-40 and 5W-30 grade oils is diminishing, while there is a growing popularity of 0W-20 oils. Japanese original equipment manufacturers (OEMs) have already approved the use of 0W-8 grade oils, and European OEMs are currently conducting tests on 0W-12 oils. For the railway industry, transitioning to lower-viscosity oils presents challenges due to the coexistence of older and newer locomotives within a given fleet. However, the potential for improved fuel economy alone makes it worthwhile to explore the use of lower viscosity oils in newer locomotives. Drawing from the success of lower-viscosity automotive engine oils, achieving a fuel economy improvement of 2 to 3% in locomotive engine oils should be feasible [10]. For railways, such improvements would result in significant cost savings, considering that fuel constitutes a major portion of their overall operating expenses. It must be noted that transitioning from an SAE 40 or 20W-40 grade to a lower viscosity grade such as 5W-30 oils will require the redesign of key engine components. The pursuit
LUBE MAGAZINE NO.177 OCTOBER 2023 33
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