If large cargo and container vessels opt for the use of two fuels, the need could arise to use different motor oils to cope with the conditions inside and outside the ECA. On the high seas, oils with a high TBN (TBN 100 to TBN 140) would still be necessary, to be used with HFO, and oils with a lower TBN (TBN 40 or lower) when the boats switch fuel in the ECAs, with special attention being paid to the necessary cleanliness and protection when using LNG, since the continued use of an oil with a high TBN with these fuels could give rise to the formation of residue on the piston assembly, which would lead to very high wear in the cylinder. In short, we would have to change the lubricant on board each time the fuel being used is switched over.

Cold corrosion, another key factor to be taken into account
In the face of increasingly restrictive environmental restrictions and the pressing need to reduce operating costs, shipowners are considering options such as investing in new motors with longer piston strokes or modifying existing motors to allow them to operate at low loads (also known as slow steaming).
Although these strategies reduce the fuel consumption, they are also prone to suffering from so-called ‘cold corrosion’, caused by water condensation in the coldest areas of the cylinder walls. This water reacts with the sulphur dioxide in the combustion gases to form sulphuric acid, therefore increasing wear due to corrosion of the cast iron liners. This cold corrosion occurs even when exclusively low-sulphur fuels are used and although to prevent its effects, the only current solution is to use lubricants with a high TBN, manufacturers of additives, such as Infineum or of lubricants, such as Olipes, are now working on new ways to prevent it, with innovative formulations with TBNs lower than 100. However, these advances in lubricant formulations will have to go hand in hand with motor operating loads closer to the optimum design point and the installation of additional equipment, such as suppressors for turbo compressors.
In spite of the advances that are being made with these formulations, there is currently no universal solution, with a single lubricant for all types of fuels and operating conditions. The smartest solution, and the one we recommend at Olipes, is to pair each type of fuel to the most appropriate lubricant.
Although it is probable that original equipment manufacturers (OEMs) choose to recommend engine lubricants suitable for the most problematic fuel (HFO with a high sulphur content), we must not discard the possibility that in the future they will include this fuel-lubricant pairing in their recommendations.
*The date for the anticipated implementation of the 1st of January, 2020 could be pushed back to 2025 according to the decision taken in the upcoming revision of the regulations in 2018. The key factor to set this delay in motion will be the market availability of fuels, of LNG and of adapted lubricants, and the effectiveness of exhaust gas scrubbers.
Sources used: www.imo.org / www.dupont.com / www.dieselnet.com / www.boe.es / www3.epa.gov / www.infineuminsight.com..