Simplifying lubrication for two-stroke engines burning new fuels 

As shipowners move along their path towards decarbonisation, they are increasingly ordering newbuildings with two-stroke, dual-fuel engines capable of burning low-sulphur fuels, ULSFO, LNG and methanol. These new-generation two-stroke engines require lubricants with a lower base number, but with the ability to match the cleanliness achieved when using typical lubes of around 100-140 BN.

Siem Car Carriers, a pioneer in LNG dual-fuelled tonnage in the pure car truck carrier (PCTC) sector, received the first delivery of Chevron Marine Lubricants’ 40 BN Category II lube oil in August 2022. The new Taro Ultra Advanced 40 is specially formulated for use in MAN Energy Solutions (MAN ES) Mk 9 and newer two-stroke engines.

Starting in September, Taro Ultra Advanced 40 was available at major ports in Europe and Asia Pacific, including the bunkering hubs of Rotterdam and Singapore, according to Chevron Global Marine Lubricants general manager Pat McCloud.

After the IMO 2020 0.50% sulphur cap came into force, the Danish engine designer defined two performance standards for lube oils intended for use in its two-stroke engines: Category I lubricants were specified for use in MAN ES Mk 8 and earlier two-stroke engines; while Category II lubes were advised for new-generation Mk 9 and subsequent newer engines.

“This advanced lube reduces operational complexity for ships’ engineers and removes the need to carry multiple grades of oil”

In recent months, Chevron, ExxonMobil and TotalEnergy Marine Lubricants have all released 40 BN Category II oils for MAN ES Mk 9 engines. Until these suitable 40 BN oils were developed, MAN ES had advised ship operators to alternate between 100 BN and 40 BN oils, based on scavenge port inspections and its analysis of oil drainage samples.

In April, MAN ES granted a ‘no-objection letter’ (NOL) to Taro Ultra Advanced 40, confirming it could be used continuously, without the need to switch to high-BN lubes. This advanced lube reduces operational complexity for ships’ engineers and removes the need to carry multiple grades of oil.

“We successfully completed the development of Taro Ultra Advanced 40 and met the MAN ES Category II requirements through thousands of hours of development work in the lab and field testing, in collaboration with our technology partner and customers,” Mr McCloud said. A key requirement in the MAN ES assessment of candidate oils is that they provide the same level of engine cleanliness as high-BN lubes.

Taro Ultra Advanced 40 was tested extensively on vessels with MAN 8G80ME-C9.2 in conjunction with shipowners, including Greece’s Cape Shipping SA.

Those development and approval tests took place on vessels with two-stroke MAN 8G80ME-C9.2 engines burning VLSFO, but Taro Ultra Advanced 40 is also suitable for use with other low-sulphur fuels, such as ULSFO, LNG and methanol.

In the case of Siem Car Carriers, this versatility allows it to use Taro Ultra Advanced 40 in the two-stroke, LNG dual-fuel MAN ES 7S60 ME-C GI engines in its 7,500-vehicle PCTCs Siem Aristole and Siem Confucius.