In these days, oil cost is about 70 US dollars, but, on the day of July. 2008, it was over 140 US dollars. This coast led fisheries industry to increasement of operating coast and made public problems such as non-operation of fishing boats and lockout of the related factories. Thus this paper studies the way to use cheap fuel in order to reduce the fuel cost. Normally fishing boat use Marine Gas Oil. this study explains to use blended oil such as MF 60, 100, 180 instead of MGO.