The paper briefly describes the works and evaluations on an investigation undertaken for the utilization of low grade fuel oils applied to marine industries in Japan. The future pattern of marine fuel oil quality is considered to be getting worse year by year in view from the world oil supply and demand.For solving this problem for marine application, the Ship-Machinery Manufacturers' Association of Japan started an activity on this project in 1980 for three years program. The works being carried out are followings;(1) survey on the quality of marine fuel oils at various ports in the world, such as density, viscosity, conradson carbon residue, sediment, alminum, silica, etc.(2) survey on the correlation between the quality of fuel oils used and troubles of ship machineries(3) burning tests of low grade fuel oils (continuous and diesel combustion)(4) experimental evaluation on fuel oil treatment including the removal of catalitic fines for shipboard equipments such as centrifuges, homogenizers and filters under various treatment conditions(5) utilization test of low grade fuel oils (250 cSt, at 50°C) for one year operation done by three coastal tankers under actual service conditions.