The Lo-Density CLHR on-line electric fuel preheater automatically provides precise temperature and viscosity control of heavy oil for efficient and stable transmission from pump to burner. Viscosity is a concern for producers who burn heavy or used fuel oil in factories, where these oils are virtually unpumpable at low ambient temperatures. The lower the viscosity, the easier the fluid will flow. The correct viscosity also provides proper atomization and clean combustion of oil at the burner nozzle.