In this study, the effect of thermal-barrier-coated piston top and combustion chamber surfaces on turbocharged diesel engine performance was experimentally investigated. Satisfactory performance was obtained with TBC 1 (with coated cylinder head and valves) and TBC2 (with coated cylinder head, piston top, and valves). Compared with a standard diesel engine, engine power was increased by 2 per cent, the engine torque was increased by 1.5-2.5 per cent, and brake specific fuel consumption (b.s.f.c.) was decreased by 4.5-9 per cent. The NOx emissions were increased by 10 per cent in diesel engines with TBC coatings compared with a standard diesel engine. Experimental studies have shown that there is a reduction in smoke emissions of up to 18 per cent as a result of TBC application. © IMechE 2008.