Combustion system and method of using fuel composition as fuel for remodeled diesel engine

A method of improving fuel efficiency of a remodeled diesel engine, comprising applying a fuel composition to the remodeled diesel engine, wherein:

• the fuel composition is composed of water, a fuel oil and an emulsifying agent, the amount of water ranging from 10 wt % to 90 wt % based on 100 wt % of the combination of the water and the fuel oil and the amount of the emulsifying agent ranging from 0.5 wt % to 10 wt % relative to 100 wt % of the combination of the water and the fuel oil, the emulsifying agent being one of an amphiphilic compound, a mixture of a lipophilic compound and a hydrophilic compound, and a combination thereof, wherein the amphiphilic compound includes an organic base having a base function group and a C3 to C20 alkyl group, the lipophilic compound includes sorbitan ester, and the hydrophilic compound includes polysorbate;
• the remodeled diesel engine comprises a cylinder unit and a combustion chamber defined by the cylinder unit, the cylinder unit having an inner surface facing the combustion chamber, a catalyst being coated on the inner surface and being selected from the group consisting of a metal, an alloy of the metal, a composite containing oxides of the metal, a salt of the metal and combinations thereof, the metal being selected from the group consisting of platinum, nickel, cobalt, copper, molybdenum, titanium and combinations thereof.