Abstract: A method is provided for automatically determining an optimum gas injection rate for a gas-lifted oil well. The optimum gas-lift slope for the oil well is initially provided and stored in the memory of a programmable logic controller. A lift gas is injected into the well at an initial gas injection rate to displace a liquid at an initial liquid production rate from the well. The initial liquid production rate and initial gas injection rate are stored in the memory. Thereafter, the lift gas is injected into the well at a first incremental gas injection rate differing from the initial gas injection rate by a first incremental value. Additional liquid is displaced from the well at a first incremental liquid production rate and the first incremental liquid production rate and first incremental gas injection rate are stored in the memory. The first incremental slope is determined from the stored data points and compared to the optimum gas-lift slope.