Originally Posted by noelex 77
There is a good article here:
Oil for yacht engines
The most important thing is to change the oil
There is an argument that high performance oils (full synthetic) are not beneficial and may even be harmful for our yacht engines.
It is difficult to evaluate these claims, but a good quality mineral oil
of the right grade, changed frequently seems the best option.
That link makes some seemingly contradictory arguments.
Yacht auxiliary engines generally run for short periods, at lower temperatures than any other duty, and typically in the lower half of their rev range. From a lubricant point of view this is a very undemanding duty, accounting for their low API requirement. Combustion temperatures never reach levels at which a high-performance lubricant can be effective, so the overall chemistry in this area is not neutral but alkaline (basic). There is a great deal of evidence to show that use of an oil with a TBN that is too high for the duty can lead to several problems, particularly high wear rates of cylinder bores.
My assumption is that the OP's new engines are for moving the boat, not as an auxiliary. The link does state that the latest diesel
rated oils have a lower TBN because of ULSD which I have seen in my UOA. So he seems to be arguing that high TBN oils are bad, yet the newer rate oils do not have high TBN.
My truck engines have been turbo charged by my tractor is not. I would think the tractor engine
runs more like a boat engine
since I set the throttle and seldom change the RPMs, unlike the truck engine which has RPM
all over the place.
One thing I have learned via UOA is to avoid "idling" since it leads to fuel
in the oil. I have hit this on my truck engine when I had to travel a route
with heavy stop and go traffic as well as my tractor engine where I was running the RPMs at a speed that worked well for the work I was doing. I would run the tractor at 1600ish RPM
but after getting fuel
in the oil, I kicked up the RPMs to 1800-2000 which solved
the fuel in oil problem. The fuel percentage in the oil was never bad enough to hurt the engine, thankfully, but I sure did not want the fuel in the oil. My route
with the truck changed so I avoided the extended idling.
Again, I run synthetic's because I run my oil longer than the manual states, for better cold weather
starts, and better MPG. Not sure how relevant that would be for a boat engine.