In response to studies done by engine manufacturers MAN Diesel and Wärtsilä, top marine lubricants suppliers are making a big shift toward higher base number oils in order to deal with the growing issue of “cold corrosion.”
This issue is primarily due to lower temperatures and higher pressures found within newer 2-stroke engine designs, noted BP Castrol Marketing Director Jonathan Hutchinson in a conversation last week in Shanghai. When burning heavy fuel oil inside these engines, the cylinder temperature is dropping below the dew point of the sulfuric acid formed in the combustion process, and it is condensing inside the cylinder, vice fully escaping from hotter burning and lower pressure engines. This is leading to increased cylinder and piston ring wear, notes Hutchinson.
To combat this issue, most lubricant manufacturers have seemed to accept the fact that the fundamental issue is that there’s not enough base additive in the oils in order to counteract the acid. The solution for some suppliers has been to simply add more additive and call it good, yet Hutchinson notes that the Castrol Cyltech CL 100 oil is based on chemistry that they have been developing over the past two to three years includes not only higher base number to control cold corrosion, but additional additives to better control deposit formation within the cylinder as well as more effective film formation to better protect wear in the piston/liner area.
The new higher BN oil isn’t for everyone though. Depending on how old your engine is, whether in the 5-15 year group, 2-5 years, or newer, there are different solutions, so it’s best to speak with your specific lubricants supplier to get their recommendations.
Another option that some shipping companies may choose is to just stick with what they’re using if they are close to a planned yard period. Hutchinson admits that the extra additives bump up the price on this new 100 BN oil, and depending on the circumstances, it may be more economical to accept some additional cylinder liner wear than to immediately switch to the new lubricant.
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