Mitsui O.S.K Lines trial indicates engines running on LNG are compatible with high BN

clean piston ring grooves

Mitsui O.S.K Lines trial indicates engines running on LNG are compatible with high BN lubricants such as Mobilgard™ M430

As a result of sulphur-free fuel not requiring a lubricant with sulphur neutralising additives, engines running on LNG customarily use an oil with a low BN. Previously, it had been assumed that additives in high BN products would accumulate without the presence of sulphur, creating problematic deposits. With this in mind, many vessel operators running dual-fuel engines swap lubricants when they change between fuels.

Breaking with this convention, in 2015, Mitsui O.S.K Lines chose to exclusively use

Mobilgard™ M430 lubricant in the medium-speed, dual-fuel engines used in its LNG tankers Hela and Gigira Laitebo.

Mobilgard M430 is a 30 base number (BN) lubricant designed for medium-speed engines running on heavy fuel oil (HFO). Although predominantly running on LNG, this oil was chosen to ensure full protection for the period the engines ran on HFO or distillate fuel.

Both tankers were inspected during routine maintenance after each running for around 18,000 hours. The inspection, and ExxonMobil’s Mobil Serv℠ Lubricant Analysis results, demonstrated Mobilgard M430 lubricant’s capacity to provide excellent, trouble-free, long-term protection for dual-fuel engines running predominantly on LNG.

Results showed no issues with the oil or wear levels and Mitsui O.S.K Lines LNG confirmed that it had not undertaken any extra servicing during standard engine overhauls. The operator was happy with the fleet’s reliability and was very pleased with the level of cleanliness. Looking at the reports from Spirit of Hela’s 16,500-hour standard service, ExxonMobil engineers noted that the engine’s piston rings were exceptionally clean.

These findings indicate that it is possible for operators to use a single lubricant for their dual-fuel engines, removing the need to switch oils at fuel changeovers while also streamlining inventory, saving both time and cost.

Note: Not all engines may see the same outcomes; results are based on good maintenance and operating procedures.