Diesel mechanics in India diagnose, overhaul, and maintain commercial diesel vehicles — trucks, buses, tractors, construction equipment, marine engines, and diesel generators — at OEM-authorised service centres (Tata Motors, Ashok Leyland, Mahindra Commercial Vehicles, Eicher/VECV, TAFE, Escorts Kubota), fleet workshops, government transport corporations (KSRTC, MSRTC, DTC), and independent road-transport workshops. The standard entry path is a 2-year ITI Mechanic Motor Vehicle (MMV) or Mechanic Diesel trade from an NCVT-affiliated institute, followed by a 1-year apprenticeship at an OEM dealership or transport company. BS-VI emission norms (effective April 2020) have fundamentally transformed the trade: every diesel mechanic must now understand Diesel Particulate Filters (DPF), Selective Catalytic Reduction (SCR) with AdBlue dosing, Exhaust Gas Recirculation (EGR), and common-rail direct injection (CRDi) systems — and use OBD-II/OBD-III compliant scan tools rather than relying on mechanical intuition alone. Senior technicians at Tata's PSE (Product Support Engineer) track or Ashok Leyland's ASTE programme earn OEM-certified Master Technician grades that unlock workshop foreman, fleet-management, and GCC-migration pathways. Diesel generator and mining-equipment specialisation at BHEL, BEML, Caterpillar, and Cummins facilities adds another premium layer.