A device for dispensing a liquid additive in a fuel circulation circuit for an internal combustion engine, in particular for an engine equipping a vehicle, said device comprising: - a tank containing the additive, - an enclosure communicating with the fuel circulation circuit and inside which the tank containing the additive is inserted, at least one movable sealing wall between said enclosure and said tank providing a sealing separation on the one hand and maintaining an identical pressure between the additive in the tank and the fuel in the enclosure on the other hand, - means for injecting the additive connected to the tank and the fuel circulation circuit and making it possible to dispense the additive in the fuel circulation circuit, said means including a dispensing channel connecting the tank and the fuel circulation circuit, and - means for controlling the injection means, characterized in that it further includes: - a temperature sensor intended to indicate the temperature of the fuel in the fuel circulation circuit, in particular near the dispensing channel, and/or of the additive, the temperature of the additive and/or the fuel constituting a parameter representative of the evolution of the additive flow rate and/or the use of the vehicle and/or climate conditions; and - pressure sensors measuring the pressure at an additive dispensing orifice positioned at one end of the dispensing channel situated at the fuel circulation circuit, and at an inlet orifice for the fuel positioned upstream from the dispensing orifice in the circulation circuit, a pressure difference between the orifices constituting a parameter representative of the use of the vehicle and/or the evolution of the additive flow rate and/or the travel conditions; the control means being associated with: - means for analyzing at least one parameter representative of the use of the vehicle; and/or - means for analyzing the travel conditions of vehicle, and/or - means for analyzing the evolution of the quantity of fuel contained in a fuel tank, said tank being accessible to a user so as to add fuel, and/or - means for analyzing the quality of the fuel, and/or - means for analyzing the polluting emissions resulting from the combustion of the fuel in the engine and/or - means for analyzing the quality of the regeneration of a particle filter positioned in the exhaust line of the engine, and/or - means for analyzing the type of additive used, and/or - means for analyzing the evolution of the additive flow rate dispensed in the fuel circulation circuit, and/or - means for analyzing climate conditions, to monitor the operation of the injection means. - a tank containing the additive, - an enclosure communicating with the fuel circulation circuit and inside which the tank containing the additive is inserted, at least one movable sealing wall between said enclosure and said tank providing a sealing separation on the one hand and maintaining an identical pressure between the additive in the tank and the fuel in the enclosure on the other hand, - means for injecting the additive connected to the tank and the fuel circulation circuit and making it possible to dispense the additive in the fuel circulation circuit, said means including a dispensing channel connecting the tank and the fuel circulation circuit, and - means for controlling the injection means, characterized in that it further includes: - a temperature sensor intended to indicate the temperature of the fuel in the fuel circulation circuit, in particular near the dispensing channel, and/or of the additive, the temperature of the additive and/or the fuel constituting a parameter representative of the evolution of the additive flow rate and/or the use of the vehicle and/or climate conditions; and - pressure sensors measuring the pressure at an additive dispensing orifice positioned at one end of the dispensing channel situated at the fuel circulation circuit, and at an inlet orifice for the fuel positioned upstream from the dispensing orifice in the circulation circuit, a pressure difference between the orifices constituting a parameter representative of the use of the vehicle and/or the evolution of the additive flow rate and/or the travel conditions; - means for analyzing at least one parameter representative of the use of the vehicle; and/or - means for analyzing the travel conditions of vehicle, and/or - means for analyzing the evolution of the quantity of fuel contained in a fuel tank, said tank being accessible to a user so as to add fuel, and/or - means for analyzing the quality of the fuel, and/or - means for analyzing the polluting emissions resulting from the combustion of the fuel in the engine and/or - means for analyzing the quality of the regeneration of a particle filter positioned in the exhaust line of the engine, and/or - means for analyzing the type of additive used, and/or - means for analyzing the evolution of the additive flow rate dispensed in the fuel circulation circuit, and/or - means for analyzing climate conditions,