TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The catalyst is a supported metal heterogeneous hydrogenation catalyst containing base metals nickel (Ni), copper (Cu), cobalt (Co) and chromium (Cr) and/or precious metals platinum (Pt), palladium (Pd), rhodium (Rh) and ruthenium (Ru) supported on alumina, titanium dioxide, silica, aluminum silicates, zeolites, magnesium silicate and active carbon or more preferably, the catalyst is a heterogeneous catalyst containing Ni, Pd or Rh supported on silica or carbon.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): Preparation of (I) or a mixture of the ethers involves reacting a 5-(alkoxymethyl)furfural (III) or a 2,5-bis(dialkoxymethyl)furan (IV) under hydrogenation conditions. Preferred Process: In the process for preparing (I), the reaction is carried out in the presence of a homogeneous or heterogeneous hydrogenation catalyst. The reaction is carried out at 50-400 (preferably 80-250, especially 100-150) degrees C at a hydrogen pressure of 1-100 (preferably 5-15) bar, where the molar ratio of hydrogen to furan derivative is not less than 5. The 5-alkoxymethyl furfural (III) and/or the 2,5-bis(dialkoxymethyl)furan (IV) used in the hydrogenation, is or are prepared by reacting a fructose and/or glucose-containing starting material with an alcohol in the presence of a catalytic or sub-stoichiometric amount of heterogeneous acid catalyst. Preferred Definitions:    R=linear or branched 1-12C (preferably 1-4C) hydrocarbyl group.    SPECIFIC COMPOUNDS - 3 Compounds are specified as (I) i.e. 2-(ethoxymethyl)-5-(methoxymethyl)tetrahydrofuran (Ia); bis-2,5-(ethoxymethyl)tetrahydrofuran; and bis-2,5-(methoxymethyl)tetrahydrofuran.    EXAMPLE - A 0.1 vol.% blend of 5-(methoxymethyl)tetrahydrofuran, and similar blend with 5-(ethoxymethyl)tetrahydrofuran were prepared with an additive free diesel fuel at an outside laboratory for cetane determination according to an ASTM D 6890 certified method. While the reference additive-free diesel showed an average cetane number of 52.5, whereas, 0.1 vol.% of the 5-(alkoxymethyl) tetrahydrofuran blends showed an increase with 0.5-1.0 to an average cetane number of 53.0-53.5.