NOVELTY - Vegetable oil based fuel (2) comprises (wt. %) vegetable oil (greater than 60), and vegetable based organic solvent (1-5). The vegetable based organic solvent comprises a terpene compound.    USE - The fuel is useful for diesel engine (claimed), particularly for operating diesel engine.    ADVANTAGE - The invention provides inexpensive, efficient and environmentally friendly alternative to petroleum derived diesel fuel. It is produced from renewable natural resources as replacement for conventional petroleum based diesel fuel that can be used without further modification. It reduces problems associated with disposal of waste vegetable oil, e.g. increasing rodent populations in sewers, and jellyfish populations at sea fed by waste vegetable oil. It provides optimum operating conditions for vegetable oil based fuel during use in diesel engine arrangement.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) operating a diesel engine (1) comprising providing the above fuel, heating the fuel prior to injection into the diesel engine, and injecting the fuel into the diesel engine;    (2) fuel system for providing a diesel engine with a fuel comprising a fuel tank containing a fuel, an engine cooling system (5) comprising a recirculating engine coolant, a fuel line (3) connecting the tank with the engine, and a fuel filter (4) arranged on the fuel line, the fuel filter is arranged with the cooling system to allow heat transfer in the fuel filter from the recirculating; and    (3) producing a vegetable oil based fuel for use in a diesel engine comprising providing a vegetable oil, filtrating the vegetable oil under a pressure A, filtrating the vegetable oil under a pressure B, and mixing the vegetable oil (1-5 wt.% based on the total weight of the fuel); the pressure A is higher than the pressure B.    DESCRIPTION OF DRAWING(S) - The figure shows a scheme of the components in a fuel system.    Diesel engine (1)    Vegetable oil based fuel (2)    Fuel line (3)    Fuel filter (4)    Engine cooling system (5)    Electromagnetic three way (10)