Viscosity is a property of all fluids and the higher the viscosity the slower the fluid moves due to the cohesion influences between the fluid molecules and the adhesion influence between the hard surface and the fluid. The physical property of all fluids is that at higher temperatures the viscosity decreases and friction is lesser between fluid layers. Therefore, on ships such as the Sapphire Princess, the fuel is heated by a viscometer to reduce the viscosity and bring it to the engine more easily. The maintenance of the desired fuel temperature is maintained by heaters connected to the PID controllers. In practice, the PID controller controls a control valve that limits the amount of steam that will heat the fuel. On the Sapphire Princess, the fuel temperature and viscosity are regulated by a rotary viscometer and a control valve that controls the amount of steam that will heat the fuel. The same regulation can be performed with electric heaters that are regulated on a similar principle as the control valve. PLC allows easier control of regulation and monitoring. Therefore, in this finishing work, a PID controller is used using a PLC and the temperature is regulated and the entire system is monitored with an HMI screen.