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Old 16-10-2017, 20:55   #91
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Diesel Engine Oil Change Frequency?

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Originally Posted by Exile View Post
I always assumed the black oil was related to the age of the diesel engine, and attributable to more blow-by as rings, valves, cylinder walls, etc. slowly deteriorate. My genset & truck engine are both quite old and the oil turns black almost as soon as I change it. But my propulsion engine is newly rebuilt and with only 400 hours the oil still stays clean looking. Doesn't seem to make any difference performance-wise, although the two older diesels do use some oil now whereas the new one doesn't. Not sure the color/appearance alone is either here nor there w/o further analysis.


Your are correct, a good “tight” engine with little blow by will not turn its oil black for quite awhile, an old well worn engine’s oil will go black almost instantly.
But there is more to it than that, an old design is designed to consume some oil and once an engine begins to consume oil its upper cylinder wear rate drops drastically. Reason is the compression rings are better lubricated if just a tiny bit of oil gets by the oil control ring. These engines also have more blow by from the beginning.
A modern oil control ring is actually three pieces, two very thin scraper rings and a spreader part that provides a path for the oil that is scraped off to return through the piston.
Old engine designs, like an old Mercedes car engine, as in the old four cylinder ones, had a one piece iron oil control ring, they were meant to burn a little oil and brand new perfectly built engines would consume some oil.
Different animal but the average aircraft piston engine is perfect shape will often consume a quart for every ten hours of running, it’s designed to.

Also oil is definitely recycled, it’s actually usually sold too. I used to collect it on the farm and when I filled a 55 gl drum the oil recycler would come by and pick it up and leave a check. It’s not a whole lot of money, but that oil is not thrown away, it’s resold, it’s often the odd brand inexpensive oil you will find, it’s not Rotella or Delo etc. So please do give it to the Marina, but do not let any water get into it, apparently that makes it more difficult to recycle for some reason.
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Old 16-10-2017, 20:59   #92
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Re: Diesel Engine Oil Change Frequency?

An old well worn engine will turn its oil black very quickly. It’s contaminating the oil with combustion byproducts and these form acid etc.
It’s for this reason that an old well worn engine should have shorter oil change intervals than a new engine.
However almost always that is not what happens, people will baby and take care of a new shiny engine, but often neglect the old ugly one.
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Old 17-10-2017, 09:04   #93
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Re: Diesel Engine Oil Change Frequency?

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Originally Posted by a64pilot View Post
An old well worn engine will turn its oil black very quickly. It’s contaminating the oil with combustion byproducts and these form acid etc.
It’s for this reason that an old well worn engine should have shorter oil change intervals than a new engine.
However almost always that is not what happens, people will baby and take care of a new shiny engine, but often neglect the old ugly one.
Your last sentence must be talking about me. The old ugly one.
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Old 18-06-2018, 11:54   #94
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Re: Diesel Engine Oil Change Frequency?

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Finally, I do not believe the savings of natural motor oil over synthetic oil is enough to warrant not using synthetic oil.
I've been told that putting Synthetic Oil into a Yanmar Marine Diesel would harm the engine.

Don't have direct knowledge, but that's what I was told by some people standing on boats.

What's the right answer?
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Old 18-06-2018, 12:35   #95
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Diesel Engine Oil Change Frequency?

Synthetic oil of the correct type and viscosity will not harm any internal combustion engine.
You won’t find a pure synthetic aircraft oil, but that is because it’s incompatible with lead, but as we don’t burn 100LL that is irrelevant.
However it’s very likely that you may not see any real advantage to a good synthetic cause most of our engines just don’t run at the temperatures and pressures that require a synthetic oil.
But they do no harm.
For years there has been this myth of don’t run a synthetic in a new engine, it won’t break in if you do. Well for decades many new cars come with synthetic oil, and they break in just fine.
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Old 18-06-2018, 13:35   #96
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Re: Diesel Engine Oil Change Frequency?

dave-
The right answer might be to call Shell or Mobil and ask them if a specific oil is correct for a specific use. For instance, "SI" gasoline engine oils are not suited for "C" Compression (diesel) engines, and vice versa.
When the correct oil is used, most brand name oil companies will in fact guarantee the performance of their oil, to certain specs, and will actually promise to replace an engine if the maker claims their oil killed it.
You hear all sorts of things like "synthetic oil eats engine gaskets" "it leaks too much in my engine" yadayada. People forget, sometimes simply using a good detergent oil will eat away old crud that was previously stopping leaks. Subtle issues like that, where "synthetic" is really not the meaningful part of the equation.
Anyone "in the business" who gets paid to rebuild worn engines, or simply paid to change the oil in engines, is going to see less busine$$ when synthetics are used. So, you might argue that they have good reason to say synthetics are no good, and you should just keep doing more frequent oil changes and spending more time and money with them. Hmmm.
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Old 18-06-2018, 13:59   #97
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Re: Diesel Engine Oil Change Frequency?

I've always sworn by Rotella T 15w40. Real oil.
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Old 18-06-2018, 15:51   #98
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Diesel Engine Oil Change Frequency?

Shell as in Rotella also makes an excellent synthetic 5W-40 T6.
I used it in my truck and my cars for years, and was using it in my boat as I had one oil for every motor, dinghy, Honda generator, generator etc.
Still run it in our little Mazdaspeed Miata turbo.
I still think it is an excellent oil, but now I am using straight weight 30W Rotella oil.
Rotella as it is very widely available. I think Chevron Delo is as good an oil.
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Old 18-06-2018, 22:28   #99
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Re: Diesel Engine Oil Change Frequency?

dave777....I've been told the same thing by 2 different well-recognized Yanmar mechanics--in 2 different countries. Their advice-I should not use any synthetic oil in my 1989 4JH-TE, even though I have done a complete overhaul on it less than 600 hours ago. Based on their recommendations we have shyed away from using any synthetic oil since. It would be nice to answers and reasons direct from Yanmar, but so far that has happened.
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Old 19-06-2018, 00:29   #100
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Re: Diesel Engine Oil Change Frequency?

In a marine engine synthetic oil doesn't make a difference. It's not the oil that wears parts. It's dirt in the oil and too much heat. Unless you run a turbo diesel flat out, all the time, marine engines run much cooler than hyway engines.

What does make a difference is clean oil. Bigger full flow filters, bypass filters or centrifuges. Many heavy diesels have 2 or more main filters in a manifold dividing the flow among those filters to slow the flow in each filter. The slower the oil goes thru the filter the more dirt, and smaller particles the filter can catch. That's why bypass filters can catch debris down to 1 micron while most full flow filters can't grab anything smaller than 30 microns. And with spin on filters, if you let the oil get too dirty, the filter plugs up and the internal bypass opens. Then you have unfiltered oil circulating. Also the dirt gets deposited in the pan and oil passages. That's one of the reasons most diesel oil turns black fast.

I had a business and one part was rebuilding marine engines. I've personally done some hundreds. About 10% were out of vessels I owned and I knew the hours and history. Maybe half of the rest were for people I knew well and I also knew the engine history. My engines and the ones owned by responsible operators with good maintenance practices generally got double the hours between overhauls than the owners that put off oil changes or ran the hell out of their engines or both.
With Detroit Diesels that I know well, naturals can go above 10,000 hours and turbos about 3-5000 hours. With care and some sense, double those hours. But with poor maintenance and WOT I've seen them come in smoking with 1000 hours. Depends on the model, too.
What usually wears out first and creates the need for an overhaul is the rings and cylinders. Often the bearings are barely worn and the crank still mics as standard. My 70 year old pair of Detroits still have standard cranks.
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Old 19-06-2018, 00:49   #101
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Re: Diesel Engine Oil Change Frequency?

A friend of mine,a GP was given an old Toyota Tercel by a patient, he drove it at least 5 but maybe 10 years, he only added oil when the oil light came on, the oil or filter was never changed finally traded on another vehicle!!!
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Old 19-06-2018, 02:17   #102
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Re: Diesel Engine Oil Change Frequency?

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Originally Posted by sailcrazy View Post
dave777....I've been told the same thing by 2 different well-recognized Yanmar mechanics--in 2 different countries. Their advice-I should not use any synthetic oil in my 1989 4JH-TE, even though I have done a complete overhaul on it less than 600 hours ago. Based on their recommendations we have shyed away from using any synthetic oil since. It would be nice to answers and reasons direct from Yanmar, but so far that has happened.
We have a similar aged Volvo 2003. The one year I tried synthetic I swear it was harder to start. Following year back to the El cheapo basic oil from the super market.

An interesting article:

Oil for yacht engines – Cox Engineering
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Old 19-06-2018, 06:42   #103
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Re: Diesel Engine Oil Change Frequency?

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Originally Posted by Lepke View Post
In a marine engine synthetic oil doesn't make a difference. It's not the oil that wears parts. It's dirt in the oil and too much heat. Unless you run a turbo diesel flat out, all the time, marine engines run much cooler than hyway engines.

What does make a difference is clean oil. Bigger full flow filters, bypass filters or centrifuges. Many heavy diesels have 2 or more main filters in a manifold dividing the flow among those filters to slow the flow in each filter. The slower the oil goes thru the filter the more dirt, and smaller particles the filter can catch. That's why bypass filters can catch debris down to 1 micron while most full flow filters can't grab anything smaller than 30 microns. And with spin on filters, if you let the oil get too dirty, the filter plugs up and the internal bypass opens. Then you have unfiltered oil circulating. Also the dirt gets deposited in the pan and oil passages. That's one of the reasons most diesel oil turns black fast.

I had a business and one part was rebuilding marine engines. I've personally done some hundreds. About 10% were out of vessels I owned and I knew the hours and history. Maybe half of the rest were for people I knew well and I also knew the engine history. My engines and the ones owned by responsible operators with good maintenance practices generally got double the hours between overhauls than the owners that put off oil changes or ran the hell out of their engines or both.
With Detroit Diesels that I know well, naturals can go above 10,000 hours and turbos about 3-5000 hours. With care and some sense, double those hours. But with poor maintenance and WOT I've seen them come in smoking with 1000 hours. Depends on the model, too.
What usually wears out first and creates the need for an overhaul is the rings and cylinders. Often the bearings are barely worn and the crank still mics as standard. My 70 year old pair of Detroits still have standard cranks.
Excellent post. So with our sailboat marine engines it's less about viscosity breakdown from heat/friction, and more about filtration/clean oil. Assuming frequent oil/filter changes (100 hrs?), it sounds like one significant improvement that could be made in our often small engine compartments would be a remote oil filter kit situated where a larger filter could be utilized? Not sure there would be room in many engine compartments for the dual filter bypass kits you speak of.
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Old 19-06-2018, 07:36   #104
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Diesel Engine Oil Change Frequency?

If you change your oil every 100 hours you have no need of a larger filter.
Bypass filtration is usually for extending oil change intervals, something that I don’t think most of us should go for, but they are excellent filters, just don’t extend your interval.
However a remote filter can be a delight, first easy to get to and second you mount them so the filter is upright so no spillage on removal and you can prefill the filter so the engine gets oil immediately upon start up.
It’s why I put a remote filter on my engine.
Unfortunately the O ring blew out between the adapter and the engine block. I could see no damage to anything so I scratched my head and replaced it, for it to later blow out again.
So after cleaning up a huge mess twice, I pitched it into the trash.
I’m certain is was a low quality / cheap kit, and that was why it failed.
Be nice if I could find a high quality kit, maybe one made by Yanmar?
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Old 19-06-2018, 08:10   #105
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Re: Diesel Engine Oil Change Frequency?

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If you change your oil every 100 hours you have no need of a larger filter.
Bypass filtration is usually for extending oil change intervals, something that I don’t think most of us should go for, but they are excellent filters, just don’t extend your interval.
However a remote filter can be a delight, first easy to get to and second you mount them so the filter is upright so no spillage on removal and you can prefill the filter so the engine gets oil immediately upon start up.
It’s why I put a remote filter on my engine.
Unfortunately the O ring blew out between the adapter and the engine block. I could see no damage to anything so I scratched my head and replaced it, for it to later blow out again.
So after cleaning up a huge mess twice, I pitched it into the trash.
I’m certain is was a low quality / cheap kit, and that was why it failed.
Be nice if I could find a high quality kit, maybe one made by Yanmar?
Westerbeke offers a remote filter kit for my 82B, but last I checked it was almost $900!! Nothing special looking about it either. I made my peace with expensive marine engine parts a long time ago, but can't go along with that one! But then I'm a bit concerned going aftermarket which your own experience reinforces.

Along with the benefits you describe, my understanding is that it can then be easier to fit a larger filter with more capacity. Assuming 100 hr. oil/filter changes, do you think this is also unnecessary? My concern here would be finding a replacement filter that matches the oem specs for the bypass valve, etc.
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