Through this paper, a variable displacement piston pump has been calculated and designed to be used for dosing thermostability additives. The metering pump design was performed according to the “Duwar” metering pump design. For a more detailed explanation of the need for dosing pumps, the history of dosing pumps has been analyzed, mentioning the first use of dosing pumps. The dosing pumps have been divided according to the principle of work. The paper gives examples of practice and characteristics of each type of dosing pump. For the design of the dosing piston pump, it was necessary to carry out a calculation involving the piston dimensioning in terms of flow, worm gear calculations, calculation of required power of the electric motor, Losses of sliding and roller bearings. Two examples of automatic regulation are proposed, and they represent a change in flow by a variable displacement or changing the frequency of the electromotor with a frequency converter. A more detailed and recommended way of regulating the change of flow is variable displacement regulation. It has been shown that the change of flow, by changing the displacement, allows a wider range of flows than regulation by changing the speed of the electric motor with the frequency converter. A mathematical model which allows regulation of the flow rate due to changes in flow in the main pipeline was proposed and design of the pump has been altered to enable stepper motor installation.