The present invention provides a fuel oil composition, including: a fuel oil base oil having a sulfur element content of from 0.01 mass % to 0.50 mass %; and a calcium salicylate having a total base number of from 100 mgKOH/g to 1,200 mgKOH/g.

A synergistic antimicrobial composition having two components. The first component is a hydroxymethyl-substituted phosphorus compound. The second component is one of the following biocides: hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine, 2,6-dimethyl-1,3-dioxan-4-yl acetate or ortho-phenylphenol or its alkali metal or ammonium salts.