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Old 07-21-2020, 01:12 PM   #1
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Diesel Engine Oil

Changed the oil In my PerkinsMarine 4-236 and after about 39 hours of running the oil still looks almost new. This engine has over 7000 hours on it.
My old Massey tractor with a Perkins 4-108 was dirty as soon as I replaced it. Besides my marine generator which has very clean looking oil as well these are my only experiences with diesels. Is this a regular thing with marine engines. I can only guess it has something to do with the raw water cooling system a land machine doesnít have.
Thanks
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Old 07-21-2020, 05:59 PM   #2
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no....some engines blacken oil fast....and its how much oil gets left behind in pan, coolers, lines, etc.

Its also a little bit of the type of oil I gave heard.

Same with land vehicles...it varies widely.
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Old 07-21-2020, 06:07 PM   #3
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Changed the oil In my PerkinsMarine 4-236 and after about 39 hours of running the oil still looks almost new.
Did you do an oil change after just 39 hours? How are you checking the oil color?

Incidentally, oil doesn't typically circulate through the dipstick tube. If you're judging oil color by checking the oil level via dipstick, this may be misleading.
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Old 07-21-2020, 07:04 PM   #4
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When you change oil about 10% of it remains in the engine. Perhaps even 20%. This dirty oil mixes w the new. I think most of what appears to be black is carbon.

You could easily do an experiment and combine 15% dirty oil w new oil and see if it looks the same.
Dosn’t much matter to me as I often change oil in cars w/o changing the filter. On my boat the filter is small so I change it regularly. What’s important is that you have plenty of new oil coming in frequently.
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Old 07-21-2020, 07:22 PM   #5
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No, I didn’t change the oil after only 39 hours but just did some cruising on a fresh oil change and I checked the oil level prior to pulling the anchor each time we moved. I was amazed at how clean it was staying. M guessing by the responses this is not common. I’m not worried about it as the engine runs like a sewing machine, just curious. This was my first outing since purchasing last November so my history with the engine is minimal. Thanks for the responses!
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Old 07-21-2020, 07:22 PM   #6
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Oil in my 4.236 stays pretty clear through 100 hours. I had a 4.108 and it was only so-so. Years ago I had a Peugeot 504 diesel that was black-black-black the moment the oil was changed. I remember accusing a Jiffy Lube oil change place of not changing the oil and they changed it again while I watched. Still black.

Since then, I've changed a lot of engine oil in Diesels as many boats I delivered were new and the OEM specified the break in oil be swapped out at 100 hrs. All that I can remember were fairly translucent at 100 hours similar to my 4.236

Behold the mystery of Diesels.

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Old 07-21-2020, 07:43 PM   #7
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My FL 120 oil looks clean 10 to 20 hours after an oil change. I don't leave too much oil in the pan after sucking it out of the pans bottom. The drain fitting is on the starboard side of the engine and I induce a slight heel by moving weight to the starboard side before sucking out the oil.
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Old 07-21-2020, 09:08 PM   #8
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Every day something new!
Thanks all
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Old 07-21-2020, 10:10 PM   #9
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I usually run 8-12 hours after startup, the soot is mostly accumulated on startup. So the more running you do at temperature and the less short hours you run, the cleaner your oil looks. Also agree looking at your dipstick isn't a gauge of oil quality, since it's a very thin sample of your oil.

Good comments in this thread!
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Old 07-21-2020, 10:17 PM   #10
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Why wouldn't oil circulate into the dipstick tube?
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Old 07-21-2020, 10:30 PM   #11
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Why would it?
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Old 07-21-2020, 10:30 PM   #12
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It's static!
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Old 07-21-2020, 11:00 PM   #13
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There’s a certain amount of “splashing” that takes place inside the crankcase. Perhaps you’ve heard of the splash system of luberication that gets the job done in many of the cars in/from the 30’s and lawnmower engines.
In our diesel inboard engines all the oil that gets pumped to bearings goes high in the engine and flows/drips back down into the crankcase to repeat the cycle.
The air being swirled by the crankshaft and slammed back and forth by the pistons moves a lot of the falling oil all over the place. Some will find it’s way into the dip-stick hole. I’ll bet if you put your finger over the dip stick hole you’ll feel a fluttering and if you remove the dip-stick and rev the engine up oil will be spit out the top of the tube. With a very old engine you may get bathed w oil ... hot oil so don’t try it.
That’s my take on oil in the dipstick tube.
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Old 07-22-2020, 05:43 AM   #14
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Much depends on the engines filtration.


ON most full flow setups the oil gets black rapidly , with bypass filtration colorusually takes far longer.
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Old 07-22-2020, 05:45 AM   #15
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It's static!

Every time you start the engine a large amount of oil gets pumped out of the sump and to the top of the engine. Any oil in the dipstick drops and gets mixed with all the rest of the oil until you stop the engine and wait the 15 minutes or so for most to travel back to the sump.
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Old 07-22-2020, 08:51 AM   #16
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.....if you remove the dip-stick and rev the engine up oil will be spit out the top of the tube. .
That actually happened to us while cruising Desolution Sound years ago. After stopping for the night, the owner checked the oil level and left the dip stick out by mistake. An ER check later the next day found oil all over the drip pan and on the ER Floor. Now, I believe that oil does circulate in the dip stick tube as well.
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Old 07-22-2020, 06:51 PM   #17
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I donít know how long ago crank shafts were meant to splash around in the oil sump, maybe with very slow rpm engines they still do The crank should not be dipping into the oil as this can cause foaming and create cavitation in the oil pump so instead of nice pure oil you end up pumping a bubbly air/oil mixture to your bearings. Big reason to never overfill your oil sump. The dip stick is for measuring the oil levels and it certainly is a good indicator of the oil that is in the sump, you can feel it with your fingers and give it a whiff from time to time.
I check mine frequently, it might save me some money or possibly avert a disaster.
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Old 08-07-2020, 12:36 PM   #18
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that is why oil analysis were invented. Visual inspection don't mean sh!t...
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Old 08-07-2020, 01:09 PM   #19
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On my old venerable engine, oil was getting blackened almost immediately after first use. When I got my water in oil problem I did multiple oil changes in a row to clean the mess. Since my last oil change oil is staying far cleaner, and after something like 30h oil still clean. So this makes me think that, in my case, it was because a good quantity of old dirty oil was remaining trapped.
Now I am considering doing some periodic oil "washing" with 2 or 3 changes in a row to remove excess of sout.

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Old 08-07-2020, 01:20 PM   #20
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Every time you start the engine a large amount of oil gets pumped out of the sump and to the top of the engine. Any oil in the dipstick drops and gets mixed with all the rest of the oil until you stop the engine and wait the 15 minutes or so for most to travel back to the sump.
I was basing my opinion on the dipstick on a 350 V8 gas engine, where the dipstick tube runs al the way down into the bottom half of the oil pan. The point where the dipstick is marked for oil level is up inside the tube, not down in the pan where it sloshes around and is recirculated.

I can see no reason why the oil in the tube would be refreshed by the engine being run, as it doesn't circulate down the tube. JMO

Your point may very well be accurate!
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