In a pulse (or proportional) type cylinder lubrication system, the cylinder lubricant is delivered to the cylinder liner as individual timed pulses of oil, injected when the piston rings pass near the injection points, rather than being sprayed as a continuous fine mist. On modern systems the lubricators are driven mechanically from the engine (or electrically by servo motors in electronic systems) so that the quantity of oil injected is proportional, or directly related, to the engine speed and load (often with a feed-rate setting adjusted to PI = 1.0 g/kWh as a starting point). Each lubricator delivers a metered amount of oil once per revolution (or per few revolutions) at the moment the piston ring pack is positioned to receive and spread the oil around the liner circumference.

Working: oil is drawn from a header tank or a low-pressure supply and a variable-delivery piston pump (lubricator) discharges a fixed volume per pulse. The oil is led through a non-return valve to an injector nozzle fitted flush with the liner, opening into a small recess. The pulse is timed electronically or mechanically to coincide with piston ring passage so the oil is wiped over the ring contact band and distributed by ring motion.

Advantages: (1) feeds oil only where and when required, so oil consumption is reduced to optimal feed rates of about 0.5 to 1.5 g/kWh; (2) reduces the volume of unburt oil entering the scavenge space and the risk of scavenge fires and oil deposits; (3) improves distribution over the ring pack, giving a more uniform oil film; (4) reduces liner and ring wear; (5) control of feed rate and adjustment to load and fuel sulphur is straightforward; (6) reduces total oil carried and sludge generation.

Disadvantages: (1) relies on correct timing - if injection occurs when the piston is at the wrong position the oil may not be spread effectively; (2) more complex, with individual lubricators and timing equipment needing attention; (3) if the timing drive or electronics fails, lubrication may stop or be delivered at the wrong time, risking scuffing; (4) nozzles and non-return valves can block, giving a dry region of the liner.

Specific cylinder oil consumption is the mass of cylinder lubricating oil consumed per unit of engine power per unit time, expressed in g/kWh. It gives a comparable figure of oil used per unit of work done.

Measurement: over a defined period (typically several hours or a watch), record the engine brake power developed from the engine log/indicator card (or the ME/ML1 figure) and the quantity of cylinder oil consumed. For electronic lubrication systems the quantity can be read from the control system; for mechanical systems the oil drawn from the header tank - or the level drop in a calibrated tank - is measured, allowing for any flowmeter reading.

Fuel-oil-ratio method (workshop/lab): cylinder consumption g/kWh = (cylinder oil flow in g/h) / (engine power in kW). On the ship, power is computed from the propeller curve and all available data.

Suggested formula used by makers: SFOC of cylinder oil = (oil feed rate setting in g/kWh) adjusted by the load correction factor, but the actual ship measurement is:

Cylinder oil consumption (g/kWh) = (Oil consumed in grams over the trial period) / (Average brake power in kW x hours run).

Care must be taken that consumption is measured with the engine at steady load, that returned oil is not counted again, and that all six/eight/nine cylinders' lubricator deliveries are included. The result is compared with maker's recommended figures (typically 0.5 - 1.5 g/kWh for modern engines at part load) and with fuel sulphur content, increasing the feed rate in proportion to fuel sulphur to maintain BN reserve.