In large marine diesel engine, it is most general to use bunker oil as fuel for the reduction of fuel cost at present. Furthermore, if crude oil will be used as fuel in stead of bunker oil the expense of fuel would be reduced about 50 percent. In this point of view, the combustion experiments on the availability of crude oil as fuel have been carried out using the test engine. According to the experimental results, it seems to be possible to use crude oil as fuel without any reconstruction of ship hull or machinery apparatuses. Results obtained are as follows ; 1. The combustion of crude oil generally showed good results. Ignitability, fuel consumption and knocking performance of crude oil were as similar as those of diesel fuel. 2. The rate of corrosion of the cylinder liner yielded by using of crude oil was slightly more than that of diesel oil which contained same percentage of sulphur. 3. While testing being performed, inflammable gases produced from crude oil around the engine were inspected, however, it was always assured to be safe. 4. At lower temperature, paraffinic wax was educed at the bottom of the fuel tank but it did not appear to influence on practical performances.