NOVELTY - Diesel fuel comprises a fuel additive comprising at least one poly-oxa-alkane compound (I).    USE - (I) is useful: to produce diesel fuels with reduced soot formation in diesel engines; and for homogenizing and improving the self-ignition capacity of diesel fuel/alkanol mixtures (claimed).    ADVANTAGE - The diesel fuel is essentially free of toxic constituents and has reduced soot formation in diesel engines, thus resulting in lowered ignition temperature and nitrogen oxide (NOx) formation. The use of FAME increases the biogenic constituents of the diesel fuel and it also acts as a solubilizer bringing the compound (I) into a solution. In the diesel fuel, (I) is used in less concentration, preferably less than 5 vol.%, lowering the cost and the calorific value of the diesel fuel. The addition of the (I) affords monophasic diesel fuel mixtures which are of interest with regard to falling crude oil reserves, since primary alcohols like ethanol can be prepared readily and inexpensively from organic starting materials. The diesel fuel: meets the density requirements of DIN EN 590; satisfies the required cold filter plugging point in case of mixing with alkanes (high melting point) and hence enabling good filterability under cold conditions; has a flash point of greater than 55 degrees C; and a high level of ignition properties (cetane number greater than 50).    DETAILED DESCRIPTION - Diesel fuel comprises a fuel additive comprising at least one poly-oxa-alkane compound of formula (R1(-O-CH2-CHR2)m-O-R3) (I).    R1, R3 = optionally branched alkyl;    R2 = optionally branched alkyl or H; and    m = greater than or equal to 1.    INDEPENDENT CLAIMS are included for:    (1) reducing soot formation in diesel engines, comprising adding the compound (I) to the diesel fuel; and    (2) homogenizing and improving the self-ignition capacity of diesel fuel/alkanol mixtures, comprising adding the compound (I) to the diesel fuel/alkanol mixture to form a monophasic mixture.