Concern over single oils

26 Jun 2013

Castrol Marine has welcomed new guidance from Wärtsilä that undermines claims that mid-range base number (BN) oils represent a single cylinder oil solution for marine 2-stroke engines.

Castrol says that this confirms its long-held concerns that using mid-range BN cylinder oils with higher sulphur fuels when slow steaming could lead to cold corrosion.

Wärtsilä has withdrawn approval for mid-range (50-60BN) cylinder oils when used with many marine engines running on Heavy Fuel Oil of above 2.5% sulphur content.

Paul Harrold, technology manager, Castrol Marine, said: “Our concerns on catch-all, mid-range BNs for slow steaming were first prompted by our own field investigations and then confirmed by bench tests and further field trials. We have consistently argued that mid-range BN oils are not suitable for slow steaming operations on modern engines. The two leading OEMs in the market have now offered specific advice on this issue in line with our position.”

The Wärtsilä letters have been followed by key ‘single oil solution’ proponents acknowledging to customers that cylinder oils previously recommended for HFO with up to 4.5% sulphur content are now for restricted use only.

Castrol says that Wärtsilä’s restriction effectively excludes the use of mid-range BN oils for about two thirds of the fuel used in the relevant engines outside ECAs.

MAN Diesel & Turbo has already excluded mid-range cylinder oils from its approved list for newer engines.

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