How New Alternative Fuels Are Reshaping the Marine Lubricants Landscape

Base number (BN) / alkalinity

• Traditional and conventional bunkers (HSFO) higher BN oils are used to neutralize sulphuric acid.
• Risk of High BN oils: Traditionally high TBN oils are used to counter the increase in the acidity of the crank case of two stroke engines. This tradition had changed post IMO 2020 after the establishment of VLSFO. Thus, many engines were witnessing the problems of over lubrication, and this will tend to increase in due course due to the alternate fuels used. High alkalinity might lead to whitish deposits in the liners, piston crown, piston rings and eventually will lead to scuffing and abrasive wear. Issues of sticky ring, deposit pile up might be experienced.
• LNG, methanol, ammonia, biofuels: sulphur-driven acid neutralization becomes less important, so BN requirements may reduce or shift depending on the fuel and engine design. However, acid formation from combustion does not disappear entirely

Viscosity

• Fuel dilution – Traditional bunkers leaking via the stuffing box into the crank case always had an impact in the crank case lube oil leading to low flash point.  decrease in the viscosity of the crank case oil.
• Methanol and some biofuels: may increase dilution and water sensitivity, which can reduce viscosity and weaken the oil film. Fuel leakage can lower lubricant viscosity, reducing film strength and wear protection. Lower viscosity can increase the risk of bearing failure (journal bearing) etc.
• Ammonia: Ammonia has a very high affinity for water and will readily form ammonium hydroxide in the presence of moisture. In fuel systems, this can lead to corrosive aqueous phases and, if water accumulates, potential for microbial activity in fuel. Direct effects on crankcase oil viscosity are expected to be limited; the main lubricant concerns are corrosion control and managing any ammonia or nitrogen‑containing species that may enter the oil.

Corrosion control

Alternate fuels such as methanol water affinity and formic acid formation can increase corrosion risk and prone to wear. Thus, a shift in the focus from acid neutralization (still alkalinity is required based on fuel and engine design) to corrosion control carries vital importance. A new norm is emerging. Similar effects are observed with ammonia.

Detergency / dispersancy

• Traditional bunkers are stable whereas some new Alternative fuels are unstable. Combustion by products of alternate fuels result in soot deposit pile up and sludge formation (in worst case scenario). Early VLSFO operations revealed that some mid‑BN cylinder oils required reformulation to improve detergency, dispersancy, and compatibility with new fuel types. New alternate fuels demand more detergency and dispersancy lube properties to counter the excessive deposits and soot pile up.

Oxidation and ageing

Conventional fuels such as HFO and VLSFO do undergo oxidation, particularly under prolonged storage and heating, leading to sludge and deposit formation. However, some alternative fuels, especially certain biofuels, can exhibit greater susceptibility to oxidation and bio‑degradation, accelerating lubricant ageing

In summary, alternative fuels are shifting lubricant functionality from simple acid neutralisation toward broader control of viscosity, oxidation, corrosion, deposit formation, lubricity, and water tolerance. As in any industry, unlearning and relearning will become the new norm in the marine sector. A strong technical perspective is now essential as new alternative fuels gain momentum. Pricing alone will no longer be the key consideration going forward. Partnering with Geoserve adds value across all aspects and provides valuable technical insights in the bunker and lubricant procurement process. For a deeper discussion on these topics and the changes ahead, please reach out to Geoserve.