Comparative Analysis of After-Treatment System Degradation: Assessing the Impacts of Ethanol-Blended Petrol and Sulphur- Contaminated Diesel on BS6 Vehicles.

This study presents a comparative analysis of the long-term reliability and degradation of engine after-treatment systems in the context of India’s transitioning fuel landscape. As Bharat Stage VI (BS6) emission standards mandate sophisticated hardware, the chemical composition of fuel—specifically the rise of ethanol-blended petrol (E20) and the persistence of sulphur in diesel, emerges as a critical variable in vehicle longevity. For petrol-powered vehicles, the investigation highlights how higher ethanol concentrations (E15–E85) in non-flex-fuel engines induce a stoichiometric shift towards lean operation, resulting in elevated exhaust gas temperatures that accelerate the thermal sintering of the three-way catalytic converter’s wash coat. Furthermore, the hygroscopic nature of ethanol promotes moisture-driven corrosion and catalyst poisoning. In the diesel segment, the research evaluates the impact of sulphur and lubricant-derived sulphated ash on Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR) systems. High sulphur content is shown to trigger excessive sulphate ash accumulation, which remains non-combustible during regeneration cycles, leading to progressive increases in exhaust back pressure, turbocharger stress, and eventual "limp mode" failures. Using the Hyderabad urban region as a case study, a hub with a significant and growing BS6 fleet—the paper correlates vehicle population data with these failure mechanisms.