Wartsila 31

The Wartsila 31 is a medium-speed four-stroke engine with a 310 mm bore and 430 mm stroke, recognized by Guinness World Records as the world’s most efficient four-stroke diesel at a specific fuel oil consumption near 165 to 168 g/kWh. Built in 8 to 16-cylinder versions giving roughly 4.7 to 9.8 MW at 720 to 750 rpm, it comes in diesel (31), spark-gas (31SG), and dual-fuel (31DF) variants. It serves main propulsion and large genset duty, meets IMO Tier II, and reaches Tier III in gas mode or with selective catalytic reduction. The modular design targets long maintenance intervals and low through-life cost.