TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The microemulsion further comprises salts and 0.001-5 (preferably 0.05-1.2) wt.% of additives comprising ammonium salts of organic and/or inorganic acids and urea derivatives, such as ammonium carbonate, ammonium nitrate and/or ammonium acetate. The microemulsion is a single phase at at least 60-90 degrees C and a pressure of 1-2500 bar. The microemulsion comprises diesel fuel or biodiesel, as (B), ammonium salts or a short chain alkyl ammonium salt of 6-30C fatty acid, as (C), and fatty acid amine polyglycol ether or sorbitan fatty acid ester, as (D). The microemulsion contains: a mixture of 5-40 or 5-50 (preferably 5-35) wt.% of water and 1-20 (preferably 2-12 or 2-10) wt.% of ethanol, as (A); 50-90 wt.% of diesel or biomass-to-liquid (BTL), or 50-90 (preferably 40-80) wt.% of biodiesel, as (B); a salt of fatty acid (3-25 wt.%) and ammonia (0.1-2.5 wt.%), preferably a salt of oleic acid (3-20, preferably 1-10 wt.%) and ethanolamine (0.5-1 or 0.5-2 (preferably 0.2-1) wt.%) or a salt of oleic acid (5-20 (preferably 10-25) wt.%) and ammonia (0.2-0.7 (preferably 0.4-1) wt.%), as (C); 0-10 wt.% of 6-30C amine polyglycol ethers or sorbitan fatty acid ester, preferably 1-10 wt.% of oleyl amine polyglycol ether (ethoxylation degree of 2 mol), 1-10 wt.% of sorbitan monooleate or 1-10 wt.% of oleic acid diethanolamide, as (D); and 0.05-0.7 (preferably 0.01-0.5) wt.% of ammonium nitrate, as additive. Preferred Components: (A) comprises 0.01-20 (preferably 1-15) wt.% of an alcohol comprising 1-20C alkanols and alkenols and/or polyhydric alcohols, preferably ethanol. The fuel based on mineral oil is diesel fuel, gasoline (including petrol with an octane number of 91-98), heavy oil, kerosene, petroleum or heating oil. The fuel based on vegetable oil is biodiesel, rapeseed oil methyl ester and/or bio oil. The fuel produced by Fischer-Tropsch synthesis is Fischer-Tropsch (FT)-fuel such as BTL fuel and gas to liquid fuel. The amount of (C) is 3-25 wt.%. (C) comprises an ionic surfactant comprising salts of 6-30C fatty acids and/or salts of 6-30C alkyl amines, preferably ammonium salts of fatty acids and alkyl carboxylates or -nitrates of alkylamines. (D) comprises a nonionic surfactant comprising fatty acid amine polyglycol ether comprising N-alkyl-substituted 6-30C fatty amines with 2-10 ethylene oxide- and/or propylene oxide units derived N-polyglycol ether, fatty acid amide comprising a compound of formula ((RC=O)-NR1R2) (a), or sorbitan fatty acid ester comprising sorbitol with at least 6-30C fatty acid and optionally with 1-10 polyglycol ether having ethylene oxide- and/or propylene oxide units, and ethoxylates (E) and/or propoxylates (P) of alcohols including a compound of formula (Ci(E/P)j) (b).R = saturated or partially unsaturated 6-30C alkyl;R1, R2 = H, 1-4C alkyl or hydroxyalkyl or 2-10 ethylene oxide- and/or propylene oxide units derived polyglycol ether;i = 6-30; andj = 1-10. EXAMPLE - Typical composition comprised of (in wt.%): diesel (50-90); oleic acid (3-20); ethanolamine (0.5-2); oleic acid diethanolamide (1-10); ethanol (2-20); water (5-50); and ammonium nitrate (0.01-5).