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Product knowledge · Lubricant

Marine Cylinder Oil

High-BN two-stroke crosshead-engine cylinder lubricant assessed for feed-rate suitability, residual alkalinity, deposits and corrosive or abrasive wear.

Reviewed Jul 2026 · Oil Testing Atlas editorial team
Definition and scope

What this product reference covers.

Marine cylinder oil is a total-loss lubricant injected into the liner of a low-speed crosshead engine; base number and feed rate are matched to fuel sulfur, engine design and operating condition.

Types and grades

Products within the family.

Names used in commerce can overlap. Use the nominated standard and exact grade rather than relying on a generic product label.

01

High-BN cylinder oil

High-BN cylinder oil is a recognised marine cylinder oil category whose exact composition, grade limits and suitability must be confirmed from the governing specification and equipment requirement.

02

Low-sulfur-service cylinder oil

Low-sulfur-service cylinder oil is a recognised marine cylinder oil category whose exact composition, grade limits and suitability must be confirmed from the governing specification and equipment requirement rather than inferred from the generic label.

03

Ultra-low-sulfur-service cylinder oil

Ultra-low-sulfur-service cylinder oil is a recognised marine cylinder oil category whose exact composition, grade limits and suitability must be confirmed from the governing specification and equipment requirement rather than inferred from the generic label.

04

Gas-fuel-compatible cylinder oil

Gas-fuel-compatible cylinder oil is a recognised marine cylinder oil category whose exact composition, grade limits and suitability must be confirmed from the governing specification and equipment requirement rather than inferred from the generic label.

Formulation architecture

What the product is built from.

Marine Cylinder Oil formulation overview
ComponentTechnical role
Mineral, synthetic or renewable base fluidProvides the principal lubricating film and viscosity-temperature foundation.
Anti-wear / extreme-pressure systemProtects loaded contacts where the application requires it.
Antioxidant and corrosion inhibitorsControl ageing, deposits and surface corrosion.
Application-specific additivesTune detergency, friction, demulsibility, air release, tackiness or seal compatibility.
Purpose of testing

Define the decision before selecting the panel.

  1. 01

    Confirm new marine cylinder oil identity, grade and fitness for the intended application.

  2. 02

    Detect contamination, degradation, mixing or storage-related change.

  3. 03

    Investigate abnormal equipment, combustion, filtration or handling behaviour.

  4. 04

    Establish a representative baseline for later comparison.

  5. 05

    Support specification, maintenance and root-cause decisions with corroborated evidence.

Tests, methods and interpretation

What each result contributes.

“High” and “low” are directional investigation prompts, not pass/fail decisions. Corroborate them using the correct specification, baseline and companion evidence.

Marine Cylinder Oil test significance and directional causes
Test / parameterTypical methodsWhy it mattersPossible causes when highPossible causes when low
Kinematic viscosityASTM D445 / ISO 3104Confirms grade and detects dilution, shear, oxidation or mixing.Oxidation, wrong oil, soot, evaporation or heavy contamination.Shear, fuel/solvent dilution, wrong grade or lighter make-up oil.
Acid numberASTM D664Trends acidic constituents, oxidation and contamination against a new-oil baseline.Oxidation, overheating, acidic contamination or wrong fluid.Fresh oil, make-up dilution or formulation difference.
WaterASTM D6304Quantifies moisture relevant to corrosion, additive loss and film strength.Condensation, cooler/seal leak, washdown, storage or sampling contamination.Dry operation or dehydration; hot sampling can reduce free-water representation.
Elemental analysisASTM D5185 with PQ / ferrography where neededScreens wear, contaminants and additive chemistry within method limitations.Wear, corrosion, dirt, additive source, wrong oil or maintenance debris.Stable wear, dilution, filtration or particles too large for ICP response.
FTIR conditionASTM E2412 trendingTracks oxidation and selected molecular contaminants against a comparable reference.Heat, extended service, contamination or depleted antioxidant reserve.Fresh oil, make-up dilution or a non-comparable baseline.
Base number / alkalinity reserveASTM D2896 or ASTM D4739, selected consistentlyTracks alkaline reserve used to neutralise combustion acids in engine and marine cylinder oils.Fresh high-BN oil, excessive make-up, wrong product or contamination with a higher-BN lubricant.Acid neutralisation, extended drain, severe combustion loading, low-BN make-up or wrong oil.
Ferrous debris / PQ indexDirect-reading ferrous density / PQ method; laboratory procedureResponds to ferromagnetic debris including particles larger than routine ICP can efficiently detect.Active gear, bearing, liner or steel-component wear; corrosion scale or maintenance debris.Stable wear or little ferrous debris; a low value does not exclude non-ferrous or very fine wear.
Analytical ferrography / wear-particle morphologyASTM D7690 or documented microscopic procedureExamines particle size, shape, colour and concentration to distinguish rubbing, cutting, fatigue, corrosion and contaminant debris.More severe particles, increasing concentration or a morphology consistent with active distress.Few captured particles; poor agitation, settling or sampling away from the wear path can reduce recovery.
Soot / carbonaceous insolublesASTM E2412 FTIR trending; thermogravimetric or validated infrared procedureIndicates combustion-derived loading that can thicken oil, disperse additives and promote abrasive or deposit-related wear.Poor combustion, blow-by, over-fuelling, restricted air, extended drain or inadequate dispersancy.Efficient combustion, short interval or make-up dilution; sedimentation can bias a poorly mixed sample low.
Sulfated ashASTM D874Characterises metal-containing additive and ash contribution relevant to gas-engine deposits, emissions systems and cylinder lubrication.Higher-ash formulation, wrong oil, contamination or additive concentration.Low-ash formulation, dilution or wrong product; low ash is not automatically suitable without an approval basis.
Perspective 02

Condition-monitoring application.

Once the product is in service, the question changes from “does it meet a product requirement?” to “what has changed, why, how confident are we and what action is proportionate?”

  1. 01Use a stable, representative sampling point and document operating hours, top-ups, transfers and maintenance.
  2. 02Trend method-consistent results rather than treating one value as a complete diagnosis.
  3. 03Separate new-product conformance from in-service condition and machine-wear questions.
  4. 04Escalate correlated evidence and rate of change; confirm surprising results before major action.
Connected test references

Open the method-level detail.

Browse the complete test library →
Official orientation sources

Verify the current edition.

ISO 6743-99 — Classification of lubricants, industrial oils and related productsOfficial source ↗