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Old 06-01-2008, 07:21   #1
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Synthetic oil?

OK, I use synthetic oil in my car (Mobil-1) and pickup truck (Motorcraft) both are gasoline engines ... Does anyone have any knowledge of using synthetic oil in small deisels (my engine has 350 hours, my gen-set is 25 years old with unknown hours) .... Would it be good or bad? ..... would it extend engine life? ... would it extend the hours between oil changes? ..... would you have to do anything special to change over from conventional oil to synthetic (it seems there would always be a little of the old oil left in the engine when you change it) like change the oil, run it an hour or so then change it again? Any thoughts would be appreciated.
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Old 06-01-2008, 07:55   #2
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Originally Posted by mobetah View Post
OK, I use synthetic oil in my car (Mobil-1) and pickup truck (Motorcraft) both are gasoline engines ... Does anyone have any knowledge of using synthetic oil in small deisels (my engine has 350 hours, my gen-set is 25 years old with unknown hours) .... Would it be good or bad? ..... would it extend engine life? ... would it extend the hours between oil changes? ..... would you have to do anything special to change over from conventional oil to synthetic (it seems there would always be a little of the old oil left in the engine when you change it) like change the oil, run it an hour or so then change it again? Any thoughts would be appreciated.
This has been beat up around here a fair bit, I being one of the people who asked a similar question. Like you, I use synthetic in my vehicles, but I decided not to use it in the boat diesel. This was mostly because I don't think you should extend the hours between oil changes due to soot build up being the biggest problem with diesel oil. The most common feeling among the engine pros on this site seemed to be the engine or it's ancillary parts, if used properly (ie worked regularly) will rust out long before they wear out. Some people mention gasket leakage with older motors when switched to synthetic, others say they didn't experience it. There's also the very good advice that if it ain't broke, don't fix it.
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Old 06-01-2008, 08:23   #3
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Originally Posted by mobetah View Post
Would it be good or bad? ..... would it extend engine life? ... would it extend the hours between oil changes? ..... would you have to do anything special to change over from conventional oil to synthetic (it seems there would always be a little of the old oil left in the engine when you change it) like change the oil, run it an hour or so then change it again? Any thoughts would be appreciated.
"MYTH #8
You canít use synthetic oil in a diesel.


FACT
Synthetic oils can be, and are, used in many diesel engines. Every engine manufacturer has specific oil recommendations, and as long as the synthetic oil meets the API rating recommended for that engine, it is acceptable. For most light-duty truck diesels, this means a minimum of API CF or CD. Some folks think synthetic oils will void the warranty on a turbo-diesel, but again, if the oil has the correct API rating, no problem. If youíre still in doubt, read your manufacturerís warranty. Itís a contract between you and the manufacturer."


Here's a good article from Banks Engineering company, a leader in aftermarket diesel technology...popular with diesel trucks. Keep in mind they are talking about "today's" engines, not a 25 year old one.

Turbo Diesel Fact & Fiction | Banks Power: Turbo Diesel Fact & Fiction by C.J. Baker
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Old 06-01-2008, 09:28   #4
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No one on here said it can't be done, it's just that economically it probably doesn't make sense unless you extend the oil change intervals. Extending the intervals seemed to be generally viewed as a bad idea. I am a huge synthetic oil fan, mostly because of its cold weather properties since we live in really cold weather 6 months of the year. The low pour point makes cranking an engine at minus 30 a lot easier and the initial startup wear is reduced greatly. But it just didn't seem to make sense to me in the boat diesel application unless you put in some kind of really high end filtration system capable of removing the soot.

It's really personal choice, if you like it and can afford it, then use it.
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Old 06-01-2008, 09:41   #5
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Most mechanics I deal with suggest that the cost of synthetics do not justify their use in small diesels for boats. Not that you can't use them but that it does not make good sense economically and really does not prolong the life of the engine.
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Old 06-01-2008, 10:59   #6
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Most mechanics I deal with suggest that the cost of synthetics do not justify their use in small diesels for boats. Not that you can't use them but that it does not make good sense economically and really does not prolong the life of the engine.
Otoh, I have been told by marine mechanics that synthetics can greatly extend the life of your transmissions, especially those like the Hurth which has a kind of skimpy capacity to start with.


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Old 06-01-2008, 11:12   #7
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Otoh, I have been told by marine mechanics that synthetics can greatly extend the life of your transmissions, especially those like the Hurth which has a kind of skimpy capacity to start with.
seer
That topic was debated heavily about a month ago. There should be good info available with a quick search
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Old 06-01-2008, 11:31   #8
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I am a strong advocate for use of synthic oils. Yes they do extend change intervals providing you do one thing. Regularly change the oil filter and most importantly use a very high quality filter. It is the filter that is the difficult part. Donaldson make very high quality filters and Amsoil have very high quality filters made for them. The filter needs to be two things. A very fine filtration, down to 2microns for Amsoil and a very high capacity, or surface area. It's no good capturing finer particles if it means the filter blocks up quicker. It also makes no sense in enjoying the longer life of the oil, if you are going to wave savings with that against the cost of many times more filter changes over the extended life.
The negative issues are found mainly in very worn engines. Sometimes it is the crud that is actually keeping the engine working. Putting in a synthetic can in these instances, cause the engine to start leaking and even fail, due to the fact that synthetics have excellent detergent properties and will break down the sludge and clean it away. However, if your engine is that bad, it is in dire need of overhaul anyway and should never be relied upon in a boat.
Whether you use synthetics or not, the regular change of filters and the use of a good quality one at that, is equal to the quality of the oil. However...
Synthetics give you several advantages over regular Dino oil. Firstly is the extended change interval. Some engines have been fitted in such away, that oil change is difficult at best. I am sure I have many echoing my feeling when it comes to change time.
Synthetics usually have a characteristic of having a thin film that clings to all metal surfaces when the engine has stopped. This helps reduce internal corroison of parts, especially the highly polished ones like cam surfaces and the different metals combination of piston rings and cylinder bores. Plus the film helps lubricate till oil pressure reaches all the nooks and crannies when the engine is started again.
Synthetics remain stable for a greater period of time and can deal with acid build up in greater quantities for longer. This is one of the biggest factors in changing oil, is to get rid of the impurities that no amount of filtration can remove.
And of course, better protection form high moisture contents, especially for parts below waterline that have seals to keep the water out and the oil in. Synthetics can still have lubricating properties when highly contaminated with water when Dino oil has long scince drowned.
Gearbox life and performance can be greater enhanced with synthetics. They often run cooler and this greatly enchances there life.
HOWEVER!!! just like all things, not all synthetics are created equal. So beware of what you put in.
AND EVEN MORE IMPORTANTLY!!! NEVER EVER put additives in to ordinary oil to try and raise it's quality. At least that is my personaly view.
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