Marine lubricants cover a wider range of products than most crew expect, and each type protects a different part of the vessel.
Getting the wrong grade into the wrong system causes wear, deposits or outright engine damage, so knowing what separates cylinder oil from gear oil matters as much as knowing where to source it.
Cylinder oil and its BN grade
Cylinder oil lubricates the piston rings and liner in two-stroke engines and needs to neutralise the acidic byproducts of combustion.
That neutralising capacity is measured as Base Number, or BN, and the correct BN depends directly on the sulphur content of the fuel being burned. CIMAC’s own working group guidance on fuel and lubrication confirms this relationship in detail, explaining why a 70 BN cylinder oil suits higher sulphur fuels while lower BN grades are matched to distillate or low-sulphur operation. Using the wrong BN for the fuel in use risks either corrosive wear or excessive piston deposits.
System oil and gear oil
System oil circulates through the crankcase and bearings of trunk piston engines, cooling and lubricating moving parts while staying stable under heat and pressure over long service intervals.
Gear oil is a separate product entirely, formulated for the higher loads and shock conditions found in reduction gears, steering gear and deck machinery. Choosing between synthetic and mineral base stocks affects both products, and the tradeoffs are worth understanding before ordering. Synthetic vs mineral marine lubricants covers how each performs under extended drain intervals and extreme temperatures.
Grease and specialised lubricants
Grease handles applications where a flowing oil film cannot stay in place, such as open deck machinery, winches and bearings exposed to water washout.
Grease consistency runs on a numbered scale, and NLGI, the body that sets the industry standard, publishes the full grade chart ranging from semi-fluid 000 up to the near-solid grade 6. Some applications need something more specific still.
Dielectric grease protects electrical connections from corrosion and moisture ingress rather than lubricating moving metal parts, which is why it sits in its own product category entirely.
Choosing and ordering the right products
Getting grades right starts with checking the engine builder’s specification sheet against the fuel and operating conditions a vessel actually runs.
Vessels calling Curaçao and St. Eustatius can order Shell, Total Lubmarine, Castrol and Gazprom lubricants through SeaHarbor, covering cylinder oil, system oil, gear oil and grease across all major brands.
Larger orders typically arrive as lubricant delivery by barge, with product pumping into your tanks handled directly at berth to keep cargo and bunkering operations running on schedule.
Uncertainty over which grade fits a given engine or operating profile is common, particularly when switching fuel types or extending drain intervals. Lubricant technical advice from SeaHarbor’s team helps confirm the right product before an order goes out, avoiding a costly correction after delivery.
For vessels also carrying tank cleaning or treatment chemicals alongside lubricant stock, Vecom marine chemicals are available through the same supply chain, keeping engine room and deck consumables on one delivery schedule.