When a ship runs a fixed route in a given time, two methods are proposed to reduce the fuel consumption of the ship. The first optimization policy is to keep the engine output power on a constant level, in spite of surrounding conditions, for instance, wind forces, wind directions, sea conditions, draft, fouling, …etc….The equal horse power running economizes about 0.6% of fuel consumption, comparing with the constant speed running of full load-half way and ballasted-half way. Secondly, if sea currents are known, the optimization policy is to correct the above-mentioned speed by about half of the sea currents. These methods can economize about 1.0% or more of fuel on a Japan-Persian Gulf voyage. The methods are based on the experimental equation for the fuel consumption of a ship, F_t=KV^a, where V: ship speed, K and a: constants, unrelating to ship speed. When a ship route is divided into homogeneous segments of distance D_i, where K_i, V_i and current component along the route S_i are constant, we have the following equations. D=ΣD_i, T=ΣD_i/(V_i+S_i), F=ΣD_iK_iV_i^a/(V_i+S_i) Under the restrictions of fixed D and T, total fuel consumption F is minimized with respect to V_i. Hence we get the second policy (a-1)K_i V_i^a+aK_iV_i^<a-1>S_i=constant If S_i=0, the first policy is derived.