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Old 03-27-2013, 04:07 PM   #261
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Why does a warmed up engine have less sheen then?
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Old 03-27-2013, 04:14 PM   #262
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Very simple. When it's cold the combustion chamber temperatures are not hot enough to ensure complete and even burning of the fuel that is being injected into the chambers As the combustion chamber temps come up the injected fuel burns more evenly and thoroughly until all the fuel is being burned (assuming good injector patterns and so forth) and no more unburned fuel goes out with the exhaust. At that point, no more sheen.

This is how it's been explained to me by every marine diesel professional I've talked to about this, including friends in the engineering department at Northern Lights/Lugger.

Our boat (2 FL120s) puts a significant sheen behind it when the engines are started, particularly in the winter. Within a few minutes of startup the sheen is completely gone. It's been this way for the last 14 years. And if the water's ruffled by wind or the light's not right the sheen can be pretty difficult to see.
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Old 03-27-2013, 04:33 PM   #263
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Marin I think I was the one that theorized that low compression was the cause of unburnt fuel and the sheen. Just groping for a reason.

Post #243. It's "very simple" until you factor in the synthetic oil. If that's the only apparent variable it dosn't mean another indirect variable can't bring about the change. What changes when the synthetic oil is introduced? Ther're probably are many changes most too in sequential to measure but several could be responsible for subtle changes like what Capthead observed. As soon as a change is made ther'e may not be but ther'e may and quite likely a domino effect of many changes so to write off the syn oil effect dosn't give much credit to the original poster or the scientific method. Now since the lack of compression causes the fuel sheen it seems to me that the syn oil just MAY have something to do w it. There are many Dino oil additives that are supposed to increase compression so do you think possibly syn could do that?
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Old 03-27-2013, 05:22 PM   #264
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Marin I think I was the one that theorized that low compression was the cause of unburnt fuel and the sheen. Just groping for a reason.

Post #243. It's "very simple" until you factor in the synthetic oil. If that's the only apparent variable it dosn't mean another indirect variable can't bring about the change. What changes when the synthetic oil is introduced? Ther're probably are many changes most too in sequential to measure but several could be responsible for subtle changes like what Capthead observed. As soon as a change is made ther'e may not be but ther'e may and quite likely a domino effect of many changes so to write off the syn oil effect dosn't give much credit to the original poster or the scientific method. Now since the lack of compression causes the fuel sheen it seems to me that the syn oil just MAY have something to do w it. There are many Dino oil additives that are supposed to increase compression so do you think possibly syn could do that?
Eric - Good points.

Maybe we should commission an official blind test study!

Capthead and Marin boats do this blind test.

In unmarked containers (one dino and one syn - but no one knows which is which) they get to change their oil every 25 hrs of operation. Just before changing oil at all both boats do a cold start and careful 15 minute long videos are taken at the exhaust of each (in calm waters at high noon!). Then, after 100 hrs operation and four (4) oil changes with same unmarked oil containers there is another cold start with another careful 15 minute video. We compare first video to last video to see if sheen amounts have altered... then we reveal which boat was using what type oil, dino or syn.

Marin you are a film expert... waada ya think??!!
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Old 03-27-2013, 05:57 PM   #265
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Now since the lack of compression causes the fuel sheen it seems to me that the syn oil just MAY have something to do w it. There are many Dino oil additives that are supposed to increase compression so do you think possibly syn could do that?
Eric: I didn't read Marin's post as saying "lack of compression causes the fuel sheen." Rather, I read it as "not being up to full heat, (rings, cylinder walls, etc. not expanded fully...) causes a percentage of the fuel to be "not completely burned", thus causing it to escape via the exhaust and causing the sheen. My boat (and most others I know of, excepting the electronic engines, ) act exactly the same way.

What am I missing here?
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Old 03-27-2013, 06:14 PM   #266
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Now since the lack of compression causes the fuel sheen.....
In the explanations I've been given by people in the marine diesel business for the fuel sheen on the water after a cold start NOBODY has ever said one word about compression or the lack thereof. ALL the explanations I've been given have related the sheen to unburned fuel going out the exhaust and the reason for the unburned fuel has been given as too low a temperature in the combustion chamber for complete and even burning of the fuel at first. A Ford Lehman 120 has no pre-heat, so things take a few minutes to warm up.

Our two-cylinder Onan MDJE diesel generator not only has a glow plug in each cylinder it has a pre-heater in the air intake. So things are hotter in the combustion chamber when it lights off and we have never observed a sheen on the water from unburned fuel in its exhaust. Not saying that some unburned fuel isn't going out the Onan's exhaust after a cold start, only that it's not enough to notice.

I think you guys are really reaching to relate the use of synthetic oil to a change in the compression ratio of the engine. But again, that's something you'll have to take up with the folks who design and manufacture diesel engines and so are well versed in this stuff.
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Old 03-27-2013, 06:39 PM   #267
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Ron, it's not so much a magnet as positively charged oil molecules, which are then in turn attracted to the negatively charged engine metal, (the negative terminal of the batts are connected to the engine block, right), ..............
Connecting the engine block to the battery terminal makes it negative with respect to the battery positive terminal. That is all. It's not negative with respect to anything else. Put one voltmeter lead on the engine block and leave the other disconnected. What do you read? Nothing, right? Leave the lead connected to the engine block but connect the other lead to the positive terminal of a flashlight batter. Don't connect the negative terminal of the flashlight battery to anything. again,What do you read? Nothing, right?
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Old 03-27-2013, 08:03 PM   #268
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Post 243 Marin.

Walt this is a "compression" engine. The heat caused by compression burns the fuel. BMEP ... pressure in the cylinder .. is caused by heat. The heat comes from the air being compressed. Also from the reduced volume caused by the upwards movement of the piston. Compressing the air in the cylinder raises the temp of the air hundreds of degrees. What percentage of heat is generated from each I don't know but there is a HUGE difference in starting performance w my cyl heaters on. The heat makes the difference.
Now if there was more compression from synthetic oil more heat would be generated from more compression and more complete combustion would take place. But I have no idea if syn oil would create more compression.

"What am I missing here?" Nothing except that a different oil may cause more compression, more heat and more complete combustion ... and less sheen.

Art,
Who really cares that much? I don't. I'm going to continue to run 30W dino oil and changing it almost twice as often and the filter a little bit less often. In mid-summer I will switch to 40W and I'll almost continue to use RPM Dello.
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Old 03-27-2013, 08:19 PM   #269
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Walt this is a "compression" engine. The heat caused by compression burns the fuel.
Eric: I know how a diesel ignites the fuel!

When I was an apprentice tool maker, one of the projects we had to build was a single cylinder bore and piston. The ID of the bore was ground & honed (absolutely no taper.) The piston was also ground (centerless grinder) to 1/2 -1 thousandths of an inch smaller than the bore's ID. The test the shop owner used was to put a small scrap of newspaper in the bottom of the bore, carefully insert the cylinder until it bounced on the compressed air, then hit it with a hammer. After extracting the cylinder, if the paper was charred black, we passed!

I know how a diesel works! (Whew!)
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Old 03-27-2013, 08:23 PM   #270
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I don't think the engine manufacturers would be real thrilled if their designed engine compression could vary all over the map willy-nilly because of the kind of lube oil being used.

Personally, I think this "varying compression" due to the kind of oil (assuming the correct grade of oil for the engine is being used, conventional or synthetic), is total armchair theory with no basis whatsoever in fact.

If oil made that much of a difference to compression and hence to performance and proper running, the engine people would be specifying EXACTLY what kind of oil to put in their engines. Down to the brand, composition, etc., etc., etc. But in my experience, they aren't all that picky as long as you use oil that meets their basic specs.

The only ones who seem to be picky are the makers of new engines that require the use of synthetics or you can kiss the warranty goodbye. But the fact that a Lehman 120 seems to do just fine on single weight, multi-vis, conventional and, apparently, synthetic oil tells me that the compression ratio of the engine is just not going to wander around enough to make any difference.

As Eric says, pre-heat makes a world of difference to the starting efficiency of his engine. Lehmans don't have pre-heat. So they start cold, fart a bunch of unburned fuel out the exhaust into the water for a bit, and then once they heat up to where they should be, no more unburned fuel being farted out into the water, no more sheen. If they had a pre-heat system on them they would probably fart a whole lot less unburned fuel into the water.

Seems dirt simple to me.
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Old 03-27-2013, 09:29 PM   #271
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"What am I missing here?"

Art,
Who really cares that much? I don't. I'm going to continue to run 30W dino oil and changing it almost twice as often and the filter a little bit less often. In mid-summer I will switch to 40W and I'll almost continue to use RPM Dello.

Eric...

My post # 264, to which I believe you might be referring, regarding "blind test study'... was totally tongue n' cheek! I really have no need to worry about diesel sheen on water at engine start up or at any other time. However, for good of nature it would be nice if all types of engines burned cleaner!

Which brings up questions for what is the difference between used dino and syn oils:

1. From what I understand dino oil can be cleaned back to its original condition (i.e. reconditioned) and then reused Can syn oil have that done also?
2. Which is more harmful to the environment when disposed of in ways other than reconditioning... dino or syn oil
3. Which is more harmful to the environment when emitted through exhaust into the atmosphere via burned use in running engines?
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Old 03-27-2013, 10:37 PM   #272
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Art re-refined dino oil is actually better than new oil. Don't remember the details.

Marin you're not entering into the spirit of learning here. You're 100% baugh humbug. I think the engines continue to fart (as you call it) even after warmup.

Well Walt and/or Marin lets hear your version of why Capthead experiences less sheen using syn oil. I posted mine but it's dependent on whether or not the use of syn oil increases compression enough to reduce sheen. What's yours?

Compression makes heat and heat solves the sheen problem. How does the engine w syn oil in it have more compression?

Walt I know you know how a diesel engine works but I felt I needed to get you focused on the heat part of the equation that is driving the issue of sheen.
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Old 03-27-2013, 11:01 PM   #273
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To be honest Eric, I suspect that Capt. Head "sees" less sheen either because of the conditions present when he saw less sheen or he simply believes there is less sheen because other people said there is and he wants to believe that synthetic oil is "better" than conventional oil.

Nothing against him--- we all "see" or "hear" things we want to see or hear from time to time. Wash and wax your car and it "runs" better, right? At least for awhile.

I'm not going to say he didn't see what he thinks he saw. I wasn't there. But I do think that he saw what he thinks he saw for reasons other than what he believes the reason to be (figure THAT sentence out and you get a prize).

I do not believe there is any connection between the type of lube oil in ones engine, particularly an old, inefficient clunker like an FL120, and the unburned fuel it blows out when it's cold. Now if it was just me believing that, I would take it with a grain of salt. But it isn't just me.

I first became aware of the sheen when my wife called me in a panic when I was doing a job in Germany the first winter we had the boat to tell me that when she'd started it up and gone back to check the exhaust there was this big sheen of "oil" on the water behind the boat. Naturally this got me really worried as well and I spent quite awhile that night trying to figure out how lube oil could go out the exhaust of a perfectly running engine, particularly when there was no smoke at all (my wife confirmed that). It finally dawned on me that it probably wasn't oil, it was probably fuel.

When I got home I immediately called our diesel shop and friends in the engineering department at Alaska Diesel Electric (now Northern Lights/Lugger) as well as a few other people I'd come to know over the years in the diesel engine business. And when I described what we were seeing, I got the exact same response from every one of them. It's unburned fuel from poor combustion in a too-cool combustion chamber. Don't sweat it, it will go away when the chambers get up to temperature. And sure enough, that's exactly what happened and continues to happen today.

And it happens that way every time (when the conditions are such that we can see the sheen). Doesn't matter if it's the first start after an oil change or the last start before an oil change. New oil, dirty oil, same sheen, same amount of time before it dissipates.

So those are the guys I'm going to go with on this. What Capt. Head did or didn't see, or thinks he saw, is irrelevant to me because I'm REAL confident that I got the right explanation the first time around. And, as I said earlier, I don't see the compression ratio being changed by the kind of lube oil that happens to be in the engine. Certainly not enough to change the amount of fuel being burned in the cylinders.

I'm happy to entertain "different" ideas if I think there is some merit to them or they are worth entertaining. This is a case where unless someone really credible in the engine design and manufacturing industry tells me otherwise, the sheen reduction theory being talked about here is not anything I deem wasting any time with. And I'm certainly not going to entertain the idea of changing the type of lube oil I use to pursue some perceived benefit that all the evidence I've come up with to date says does not exist.

What other people chose to do is what other people chose to do, right?
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Old 03-27-2013, 11:26 PM   #274
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Marin you're not entering into the spirit of learning here.


TF would be a difficult place to get educated on Synthetic oil vs Dino. General BS sure, but who to believe ---------- ? Having said that, three things are for sure and easily found on Cat and Chevron detailed websites:
  1. Synthetic (100% and not the blends) oils are recommended but not mandatory for cold weather start stop type operations with temps routinely below 0 degrees F. Some diesels never stop outdoors when really cold thus obviating the need for syn oil cold start advantages
  2. Today's Dino oils (such as Chevron DELO 400 Isosyns) have additives permitting warm weather synthetic advantages without the expense.
  3. Oil analysis, not at Joe's Joint either - use Cat SOS or similar, when routinely performed gives you the best possible leg up on timing for oil changes and enhanced engine longevity -
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Old 03-27-2013, 11:38 PM   #275
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What Capthead saw was not what he saw? Could be that some other variable like what time of day the "sheen" was viewed and where the sun was ect. Through no fault of his own another variable altered the visual experience and was not in fact related to the change of oil type used. Perhaps Cap could go back and do the experiment in reverse?


Well the thread's still open .........
Anybody have any test information that shows synthetic oil should boost compression? Something above a bar room half intoxicated argument and a full blown congressional investigation. closer to the latter would be beneficial.

Or does anybody have any other ideas how syn oil could decrease sheen?????
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Old 03-27-2013, 11:39 PM   #276
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Why do YOU think it boosts compression?
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Old 03-27-2013, 11:40 PM   #277
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This is getting funny. Now I'm told I don't know what I see and what I see isn't what I think.

It must be my Lying eyes....damn it!

I started this so I could talk to other synthetic users, not to convince anyone to use it. I get the picture. Nobody uses it and I am the lone wolf here.

Not a problem, I like this forum and I hope to find friends here.
Hey, Cappy, look back at my thread 249 a couple above this. I'm on you side in this. Castrol Magnatec Diesel is what you would call a semi-synthetic.
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Old 03-27-2013, 11:56 PM   #278
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Connecting the engine block to the battery terminal makes it negative with respect to the battery positive terminal. That is all. It's not negative with respect to anything else. Put one voltmeter lead on the engine block and leave the other disconnected. What do you read? Nothing, right? Leave the lead connected to the engine block but connect the other lead to the positive terminal of a flashlight batter. Don't connect the negative terminal of the flashlight battery to anything. again,What do you read? Nothing, right?
Ron, I take you point where the open circuit is concerned, but that is why the friction and heat is important. once ignition is on, the block is negative, ie. going to attract positively charged molecules, and friction and heat increases that. I think that makes sense..?

Eric, and Capthead, I have to agree with Marin here. Even tho a fan of synthetic oils to a certain extent, I don't see how they could influence compression. I think the temporary sheen from incompletely burnt fuel adequately explains it. Synthetics are an advance in the technology, for sure, but not miracle workers, and the higher cost does mean not cost effective in some cases.
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Old 03-28-2013, 12:08 AM   #279
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My interest in what Capthead saw has nothing to do with sheen or compression. He saw a 5 degree drop in his coolant temp! I don't think for a minute that he imagined that and that's the thing that interests me most! He read it off a gage! A 5 degree drop means that his engine is running cooler. Mine runs hot (192 degrees) and no pro has been able to tell me why. I'm not interested in cold starts, extending the life of my engine over one that uses Dino or improved compression. If, in fact (and I believe him) his engine temp dropped 5 degrees, he experienced some benefit in running synthetic oil! A benefit that has me very interested.

End of rant.
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Old 03-28-2013, 12:33 AM   #280
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If, in fact (and I believe him) his engine temp dropped 5 degrees, he experienced some benefit in running synthetic oil! A benefit that has me very interested.
That so far is the only relevant item I've seen worth pursuing in this whole thread Walt. If the gauge says cooler, it's cooler. If one has a motor tending toward higher temperatures like yours does it's well worth a try and see IMO. Certainly no harm will come from trying it out.

I agree with Tom(sunchaser) that if you want to see the facts you need to look at what the engine and lubrication manufacturers have to say. The problem with all the anecdotal sheen and compression claims, is it actually detracts from any real tangible benefits of the product. Wild claims don't sell mechanical and petro-chemical engineers, provable and repeatable data does. I'm sure more than one twin engine boat owner out there somewhere has already done a side by side comparison but so far none has posted here.
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