Fuel for internal combustion engines

An internal combustion engine fuel comprises a liquid hydrocarbon and a minor proportion of a hydrocarbon-soluble mixture of one or more neutral esters of a polycarboxylic acid and of one or more neutral esters of a phosphonic acid. The presence of the hydrocarbon-soluble mixture protects the exposed engine parts against corrosion and incrustation and thus prevents premature wear. The hydrocarbon-soluble mixture may also be added to mineral lubricating oils, since it influences the sliding properties of such lubricating oils and their ability to withstand pressure. Polycarboxylic acids whose esters may be employed are phthalic, iso- or tere-phthalic, naphthalene or diphenyl carboxylic, and trimellitic acids and the halogen substitution products of such acids; also adipic, pimelic, suberic, azelaic, sebacic, nonane dicarboxylic, decane dicarboxylic, hexahydrophthalic, and alkyl-naphthalene dicarboxylic acids. The phosphonic acids whose esters may be employed are benzene phosphonic, toluene phosphonic, xylene phosphonic (ethylbenzene) phosphonic, naphthalene phosphonic, alkyl-naphthalene phosphonic, cyclohexane phosphonic, indene phosphonic, dodecane phosphonic, di (chlorophenyl) phosphonic [also known as di (chlorophenyl) phosphinic], di (fluorophenyl) phosphonic and di (tolyl) phosphonic acids, as well as phosphonic acids which are substituted by radicles of petroleum fractions. The alcohols from which the esters may be derived include C1-C10 alkanols, stearyl alcohol and cyclohexanol. The esters may first be dissolved in mineral oil (e.g. spindle oil) and the solution added to the fuel. If desired, basic compounds, particularly amines, can also be added to the fuels or lubricating oils. In the examples, fuels are described consisting of benzine and (1) di (p-chloro- or fluoro-phenyl) phosphonic acid-n-butyl ester, dibutyl phthalate and spindle oil; (2) di (p-chloro-phenyl) phosphonic acid-n-butyl ester, p-chlorobenzene phosphonic acid di-n-butyl ester, methyl n-amyl adipate or methyl n-butyl terephthalate, gas oil and tetraethyl lead; and (3) p-chlorobenzene phosphonic acid distearyl ester, di-n-butyl sebacate, mineral lubricating oil and dicyclohexyl amine. A fuel consisting of diesel fuel, p-chlorobenzene phosphonic acid di-n-butyl ester, methyl n-butyl phthalate and stearylamine is also described. Furthermore, a lubricant consisting of mineral lubricating oil, p-chlorobenzene phosphonic acid di-n-butyl ester, di-n-butyl sebacate or phthalate and dicycl