Abstract: Disclosed is a diesel fuel composition obtained by mixing a diesel oil and a biodiesel oil, which can be used in popular diesel cars. The diesel fuel composition enables remarkable reduction in sludge formation. Specifically disclosed is a diesel fuel composition obtained by mixing a diesel oil containing an aromatic component and a biodiesel oil. The diesel fuel composition is characterized in that the biodiesel oil content in the diesel fuel composition is 10-50% by volume, and the aromatic component content in the diesel oil is not less than 30% by volume.

Abstract: A fuel supply system is incorporated into a diesel engine including a low-pressure fuel pump 2, a high-pressure fuel pump 3, a common rail 4, fuel injection valves 5 and a fuel return line 14. The fuel supply system reduces the discharge rate of the low-pressure fuel pump 2 supplying the fuel to the high-pressure fuel pump 3 when the diesel engine is in an idling state and the temperature of the fuel is below a lower fuel temperature threshold and when the diesel engine is in an idling state and the temperature of the fuel is above an upper fuel temperature threshold. The flow rate of the feed fuel discharged from the low-pressure fuel pump is reduced when an idling state or a specific state where the fuel is at a specific temperature. Thus the fuel line system of the fuel supply system can be built in a lightweight arrangement and the piping of the fuel line system can be simplified.

Abstract: A fuel supply system is incorporated into a diesel engine including a low-pressure fuel pump 2, a high-pressure fuel pump 3, a common rail 4, fuel injection valves 5 and a fuel return line 14. The fuel supply system reduces the discharge rate of the low-pressure fuel pump 2 supplying the fuel to the high-pressure fuel pump 3 when the diesel engine is in an idling state and the temperature of the fuel is below a lower fuel temperature threshold and when the diesel engine is in an idling state and the temperature of the fuel is above an upper fuel temperature threshold. The flow rate of the feed fuel discharged from the low-pressure fuel pump is reduced when an idling state or a specific state where the fuel is at a specific temperature. Thus the fuel line system of the fuel supply system can be built in a lightweight arrangement and the piping of the fuel line system can be simplified.