Synthetic vs. regular disel oil

manyboats said:

Marin thinks it's nuts and so do many others but I think it works well so why not do it?

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Think of it this way, Eric. You have drained your dirty oil and put new, clean oil into the engine. Would you then take a quart of the oil you just drained out of the engine and pour it back in?

That in essence is what you are doing by not changing the oil filter along with the engine oil.

Oil analysis on a regular basis is a very valuable tool to keep track of an engine's condition. While perhaps a bit apples and oranges, the various FAA-approved practices of extending an engine's TBO (time between overhauls) has as a primary requirement oil analyses performed at a prescribed interval. This is so that an increase in internal component wear can be detected before the wear becomes a threat to the engine's reliability.

While a one-time analysis does not have the overall value of analyses done over time at specific intervals, it is not totally useless. When we had the boat we ultimately bought hull and engine surveyed, the engine surveyor took oil samples from both engines and the generator and sent them in for analysis. He ran the engines up to temperature, at full throttle, and so on before taking the samples. He told us that a one-time analysis was not going to tell us anything much about the overall condition of the engine, but that it would at least show the contaminant levels in the oil at that particular moment.

The two Lehmans came back clean as a whistle but the Onan had minute traces of metal in the oil. The surveyor's report said that this was kind of the nature of the beast for this engine and it was nothing to be concerned about.

So as others have said in this thread, a one-time oil analysis is not a guarantee of anything and certainly doesn't provide the true value of periodic analyses, which is to show trends. But I think it can at least give a snapshot of the condition of the engine, particularly with regard to illustrating a higher-than-normal level of contaminants.

Marin said:

Would you then take a quart of the oil you just drained out of the engine and pour it back in?

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I agree and always change the oil filter on any engine at the time of oil change.

markpierce said:

I agree and always change the oil filter on any engine at the time of oil change.

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I would have thought that was standard proceedure. Not changing the filter would be like taking a shower and then putting your dirty drawers back on.

Re the filter change I agree it's better to change the filter.

That said I still don't believe a filter has enough dirt in it to warrant changing. Is changing the filter every 10 hrs is better yet? Why not do that? I do believe the oil needs changing more often than the filter so why should I change the filter more often than it needs to be changed? Can you imagine how much the filter industry is making from this excessive filter changing?

Re the dirty oil Marin if I did as most do ALL the oil would be dirty much more of the time and clean oil is where it's at. This is true as I change the oil more often than usual. I think the main reason I started doing this is to make oil changing simple enough so I would do it considerably more often and there-in lies the value of my practice. Pump the oil out. Put it in the recycle tank. put new oil in. As simple as that. Even clean hands all the way.

Years ago somebody told me re-refined oil is better than new oil for some specific reason. Anybody know why?

manyboats said:

Years ago somebody told me re-refined oil is better than new oil for some specific reason. Anybody know why?

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I believe the theory is that having been run through the engine, some contaminants have been burned off, then the dirty oil is subjected to centrifugal separation and filtration that makes it cleaner than original.

In terms of costs, the expense of filters or using synthetic oil is so trivial compared to most every other expense I can't think of a reason not go with the best, even when you can make the case it isn't necessary. It also isn't very expensive. When I change oil, I use synthetic because contrary to what others on the site have posted, I believe it has better adhesion than dino oil does (or at least that is what the oil expert at CAT national told me). I also change out the bypass filter and the OEM filter. Saving $60 by cutting corners on the operation just doesn't have much appeal.

Eric--- We change the oil in our Lehmans every 100-150 hours. The manual calls for an interval of 200 hours. And while the filter element may not have much "dirt" trapped on it, the filter itself is filled with a quart or more of contaminated oil. So leaving it on the engine is like putting in 11 quarts of new, clean oil and one quart of contaminated oil.

So it seems a very false economy to leave the old filter in place when one changes the engine oil. Particuarly given the insignificant cost of the filter compared to the other costs associated with owning and operating a boat.

As to changing the filter itself, it's a snap even with the Lehman's "upside down" filter mounting. We were taught a trick that totally elminates the mess of removing the filter, so changing the filter adds virtually no work to the task of chainging the oil.

So I see nothing at all to be gained by retaining the old filter with its load of contaminated oil. But if the cost and effort of changing the filter every time is more than someone else wants to deal with, that's okay, too.

Where is a reputable place to get an oil analysis done?

GonzoF1 said:

Where is a reputable place to get an oil analysis done?

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Your best bet is probably to ask a good diesel shop in your area or a local engine surveyor.

sunchaser said:

Oh, Tony Athens you say. Go to his posting #49252 with the last entry made on Feb 3 titled "MTU Oil Analysis Opinion"

Part of his comment is, "put a random oil analysis where it belongs - at the bottom of the list of things to worry about."

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Bingo. In context, he's bang on.

GonzoF1 said:

Where is a reputable place to get an oil analysis done?

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Any Cat or Detroit service center will have a sample kit.

Delfin said:

I believe the theory is that having been run through the engine, some contaminants have been burned off, then the dirty oil is subjected to centrifugal separation and filtration that makes it cleaner than original.

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My Hinos have centrifugal filters, I clean them every other oil change. The housing will have 1/8" - 3/16" of carbon caked to them. The oil stays clean looking on the dipstick way longer than other diesels I've worked on.

sunchaser said:

But an oil analysis every now and then on a few hundred hour per year (at most) toy boat engine is not as important as how the real things have been taken care of to prevent the oil from showing baddies. ......................

Oh, Tony Athens you say..................................

Part of his comment is, "put a random oil analysis where it belongs - at the bottom of the list of things to worry about."

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For crying out loud! We're operating toy boats! These are not Euclid Earth Movers that operate around the clock.....change your oil and filters frequently and be done with it.

Marin I'm taking out dirty oil. 90% of it. But who knows there may be more old oil laying in puddleing spots in your engine than in my filter. You may think your's jolly correct as you do what your'e instructed to do but your oil may be more dirty than mine. I'm actually quite sure of it.

Walt is it too slipery for you?


Just go read another thread if you doint like oil.

manyboats said:

Walt is it too slipery for you?
Just go read another thread if you doint like oil.

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Sure, Eric....I'll get right on it.

manyboats said:

....but your oil may be more dirty than mine. I'm actually quite sure of it.

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And why would that be? I put 12 quarts in and when I change it I take 12 quarts out. I know this because I dump the old oil from the pump-out bucket into the empty gallon containers that the new oil came in. And the system I use to pump out the old oil goes to the lowest spot in the sump. If I pump the old oil out and then remove the sump drain plug, nothing comes out but a few drips.

GonzoF1 said:

Where is a reputable place to get an oil analysis done?

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I get mine from American Diesel. Prepaid and not expensive. Plus they get a copy of the analysis and take a look as well, and will give you a call if they spot something that needs attention.

What if I give you the last word Marin?.

I'm fast getting to where Walt is.

GonzoF1 said:

Where is a reputable place to get an oil analysis done?

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Any CAT or DD dealer. Most any heavy equipment or trucking sales or service company or a major fuel and lube distributor.

River Cruiser said:

The oil stays clean looking on the dipstick way longer than other diesels I've worked on.

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Be careful!!! The fact that it is "clean looking" may actually be bad. I bought a sailboat from a fellow. It had a diesel and it would be the first diesel that I had owned and cared for. I realized that the previous owner used a non-diesel rated oil...just your everyday Pennzoil that you would run in your car. That oil looked clean(on the dipstick) ALL the time. After doing a bit of research I realized that the oil was not the proper oil to be running in a diesel and changed to a proper oil. Guess what??? My oil no longer "looked clean on the dipstick"!!! Why??? Because the oil was doing it's job of removing the contaminants(suspending them) endemic to diesel engines.

Baker said:

Be careful!!! The fact that it is "clean looking" may actually be bad. I bought a sailboat from a fellow. It had a diesel and it would be the first diesel that I had owned and cared for. I realized that the previous owner used a non-diesel rated oil...just your everyday Pennzoil that you would run in your car. That oil looked clean(on the dipstick) ALL the time. After doing a bit of research I realized that the oil was not the proper oil to be running in a diesel and changed to a proper oil. Guess what??? My oil no longer "looked clean on the dipstick"!!! Why??? Because the oil was doing it's job of removing the contaminants(suspending them) endemic to diesel engines.

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Good point. We have a Puradyn bypass filter with a 1 micron filter and the oil is still black even though the bypass clearly has the oil passing through it. The reason is because particles of carbon smaller than 1 micron are still sufficient to blacken the oil, but can't cause wear because they are smaller than the machine tolerances of the motor. You can't tell anything about the utility or condition of the oil from its color, other than it is or is not brand new.

So there's bad carbon and goo or harmless carbon. Kinda like cholesterol huh?
I'll bet it still cases engine wear.

Sixty grit and 800 grit still works as an abrasive.

manyboats said:

So there's bad carbon and goo or harmless carbon. Kinda like cholesterol huh?
I'll bet it still cases engine wear.

Sixty grit and 800 grit still works as an abrasive.

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Unless it never comes into contact with something to abrade. Kind of like a 1 micron abrasive particle suspended between two contact points 3 microns apart.

Delfin said:

Unless it never comes into contact with something to abrade. Kind of like a 1 micron abrasive particle suspended between two contact points 3 microns apart.

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Be careful of higher math around here...

I'm a bit familiar with the hardness scale. How can a soft soot (C) particle abrade a hard engine alloy?

I'd always thought removing soot and other particles with the filters is to insure that lubricating oil passages, rings and bearings remain free and clear and oil doesn't become too viscous due to the trash buildup.

Tom I'm w you on the later but I thought carbon was hard as in high carbon steel. I think the "soot" and carbon are both black.

Delfin how's the one micron particle know to stay in the "middle"? And the two contact points would be carbon, soot or marbles?

sunchaser said:

I'm a bit familiar with the hardness scale. How can a soft soot (C) particle abrade a hard engine alloy?

I'd always thought removing soot and other particles with the filters is to insure that lubricating oil passages, rings and bearings remain free and clear and oil doesn't become too viscous due to the trash buildup.

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Soot by itself can't cause wear since as you note, it is softer than the steel. My understanding is the same as yours - that the harm is caused not by individual particles, which are tiny, but by their agglomeration into particles large enough to inhibit oil flow between wear surfaces. The additive package in the oil is supposed to keep the agglomeration from getting out of hand.

manyboats said:

Tom I'm w you on the later but I thought carbon was hard as in high carbon steel. I think the "soot" and carbon are both black.

Delfin how's the one micron particle know to stay in the "middle"? And the two contact points would be carbon, soot or marbles?

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Is that a serious question?

The contact points would be bearing races, shafts, rings, cylinder walls etc., which as far as I know are not made out of marbles.

Let's see...1 micron would equate to about a 1200 grit abrasive, with an average particle size of about 0.00005". Now what are those bearing clearances again?