A subsea grease injection system has a grease accumulator containing a supply of grease, a hydraulic accumulator, a flowline connected to an outlet of the grease accumulator so as to allow discharge of grease from the supply to flow therethrough, and a subsea structure connected to the flowline. The hydraulic accumulator is in fluid communication with the grease accumulator such that the displacement of hydraulic fluid from the hydraulic accumulator causes a corresponding discharge of grease from the grease accumulator. The subsea structure receives grease from the flowline. The grease accumulator is a piston and cylinder in which the piston is received in the cylinder to define first and second compartments. The supply of grease is in the first compartment. The hydraulic fluid fills an interior of the second compartment. This avoids the use of hydraulic conduits from the surface such that only power and communications are from the surface.