A method for producing diesel grade fuel of plant origin by transesterifying a refined vegetable oil with a charge of a C1-C4 alcohol in the presence of a catalyst and at least 0.2 parts by volume, related to unit volume of refined vegetable oil, of an aliphatic hydrocarbon solvent with a boiling point of −42° C. to 200° C., comprises mixing the oil, alcohol, catalyst and solvent in a single reaction vessel under homogeneous conditions which promote transesterification to 95-98% completion and which suppress reverse glycerolysis, without stopping transesterification to remove by-product polar glycerol, and without subjecting the oil/fuel mixture to a further transesterification step with a fresh charge of alcohol and catalyst.