Synthetic lubricating oil for marine diesels

[freshalaska]

What are the pros and cons to using synthetic lubricating oil with marine diesels engines. Seems it would be nice not to have to change the oil as often. So what do you think?

[mike d.]

I would think your best bet would be to contact mfg. of engine to see what they recommend!

[Nineteen]

Hi

I run Mobil 1 5w40 in my Yanmar engine and its Kanzaki transmission and have done so for the last 6 years since we owned the boat. Very happy with how clean the engine is staying. 18yrs old now with 2300hrs.

I have also run the 5w50 in my wifes car for the last 20 years (supercharged 318is with 490000km now unopened) and the same in my 5.4l V8 with 289000km.

I would not hessitate running this brand in any of my small engines and use it in my Honda 2000w gen and my Honda 13hp pressure washer. All my other stuff is 2 stroke and I use synthetics in them as well.

Unless it is specifically forbidden by a manufacturer I would not use dino oil anymore. Good oil, fuel, and good filters are the secret to a happy engine.

I do the boat service every November and the cars every 15000km with factory filters. The small engines get serviced annually and I don't need to top up any of them between services.

So I guess for me that the proof is in the pudding....

BTW I don't work for any oil company and do all my own work.

I have heard all the stories but have yet to see any first hand issues with synthetic lubricants in 34 years as a tradesman.

Cheers Tom

[Flyingriki]

The first time I heard of synthetic oil was in 1974 at a motel in Nebraska. The owners husband was working the desk and he had a display of synthetic oil in the lobby. Told me he had been running his pumps for a few years on the stuff and every time he pulled one apart he was shocked (especially the first time) to find no measurable wear and reused the bearings.
We gave up on it in aviation for known and proven problems with ancient designed engines that needed different oil to stay clean, and we change it often. But nothing else I've heard of has a problem and I use it religiously in cars and bikes. Will be interesting to hear Yanmar (probably) won't allow it's use since they have never tested it and don't care to bother.....?

[captstu]

Yanmar recommends synthetic oil for our 4BY2 and 30 non-synthetic for the trans.

[Caliber40]

The mfgr will most likely say no, it's not worth it.....and so will the experts on this board......I say for the extra money (not much more) and hearing all the testimonials to synthetic I say go for it! I use in both my Turbo Yanmar and my gen set, cars, lawn mowers etc....extend interval no more than 100 hours ..... usually less depending on where I am cruising wise.

[ArmyDaveNY]

If it is under warranty make sure it doesn't void the warranty.

[bcboomer]

I think 100% synthetic may be worth the extra expense but so many "synthetics" I see are "synthetic blends". Paying a bunch more for a couple of percent synthetic makes no sense.
The most important thing today, with so many variations available, is to use an oil with the correct SAE designation for your engine.
The equally important thing is to replace it on a regular basis.

[ArmyDaveNY]

Originally Posted by bcboomer

The equally important thing is to replace it on a regular basis.

I was under the impression that synthetic oil isn't supposed to be replaced anywhere near as often as traditional oil. I was also under the impression that replacing the filters on a regular basis is very important. The theory is that the filters take out bad things like dirt and metal, while leaving the synthetic oil which is still good.

[Nightcrawler]

Ran synthetics in 3 vans/pickups for for 130,000+ miles on each. Changed oil once a year. Low consumption, excellent protection. Switched our Cummins to synthetic. They have over 4,900 hours on them. At 175 hours on new synthetic sent oil sample. Perfectly clean. Recommendation - "send us another sample in 200 hours." Twin Discs love it too.

[taxwizz]

In my Westerbreak 27 the oil filter cannot be changed without first draining the oil. Would anyone consider replacing the drained oil back into the engine after changing the oil filter?

Therefore if the filter is changed annually, the oil would likely be changed at the same time and the long life benefits would be lost.

[Wulf]

Originally Posted by taxwizz

Would anyone consider replacing the drained oil back into the engine after changing the oil filter?

Absolutely not. Think contamination control. Added risk of introducing contaminates into the system just not worth the relatively few $$ to replace the oil. Yes, you can wash & wipe out the container (are you using lint free rags?) and may be ok. But long run clean new oil from the original container is the only way to go. I do not even use a funnel for that reason. Just carefully pour straight from the jug. It can be done in most cases. Works well on my boat with very little access above the engine, truck, cars, lawnmower etc.

[taxwizz]

Originally Posted by Wulf

Absolutely not. Think contamination control. Added risk of introducing contaminates into the system just not worth the relatively few $$ to replace the oil.

I agree 110%.
Therefore, as I suggested above, by replacing the filter annually, you lose the long life benefits of synthetic oil.

[transmitterdan]

It really depends on details of the engine design. It’s best to just use the oil recommended by the engine manufacturer. Replace it on the schedule they recommend. 99% of boaters are not more knowledgeable about lubricants than the engine manufacturer.

How many small diesels die from lubricant death when oil used was as specified and changed on schedule? Probably none.

[Flyingriki]

What's the trick to getting all the oil out? And the tranny?
I need to replace both to have a starting point for a new2me boat.
Thanks!