How quickly does your diesel lube oil go black?

I have read claims that people's diesel lube oil stays cler for quite a while but after owning three diesels I have never seen oil stay clean looking very long at all.
What are your experiences?

Depends on the engine and the loading. Some 3208TA in high output apps you can change the oil three times in a row and it is black after a couple hours run. Run same engine at 1200 and it will stay clean for 20hrs.

Nothing wrong with black oil, it's just soot.

On my 450C, it is pretty black at 50-100hrs, I change it at about 300hrs.

If it bothers you, take a sample and see what the soot/insolubles are.

QSM11's, which I have owned since new, turn the oil black in about 24 hours run time, even though engines are run below 1100 rpm more than 90% of the time.

Cummins 6bt's.....The oil is pretty black after 10 hours of running them easy. Ironically, I've had 2-cycle Detroits that didn't turn black until 50 hours or so.

Mine used to blacken the oil fairly quickly. THe oil still blackens but it now takes a few more hours. By 40 or so it's black.

My Lehmans turn it black pretty quickly.

I run clean oil. I centrifuge the oil every 25-50 hours. Before the centrifuge I used add on bypass filters. I've been experimenting with running clean oil since the 1960s and my experience shows much longer engine life. Maybe more than double if you're not running high exhaust gas temperatures.
With filtering, the slower oil passes thru a filter, the more dirt it traps. That why many Detroit Diesels have transparent oil longer. Older DDs had a bypass filter and no full flow filter. Later they had dual full flow filters that slowed the flow. Many small diesels come with short spin on filters, but a longer version is usually available. Going to the longer size cuts the flow rate almost in half and catches more debris.
Fine soot eventually clumps into larger particles along with other debris and gets to a size where it causes engine wear before a full flow filter can capture the dirt.
I haven't actually changed oil for more than 5 years, just add make up oil and test 1-2 times a year. The centrifuge also removes water.

Lepke,
could you please do a thread on the centrifuge....
what it is, how it works, etc....
and let us know your findings and thoughts etc...

are they readily available, something you made yourself, expensive as all hell?

you know, just everything about it, lol

thank you! and now back to the present thread

I too would like to see more discussion about centrifuging oil. I suspect, but have nothing to back it up, that most soot is very fine, will not get trapped by the filter and will not be removed by centrifuging.

I accept Lepke's statement above that the small soot particles can clump and then can cause engine wear. But at that point won't they get trapped by the filter. And won't the dispersants in the oil keep the soot from clumping?

David

Maybe Lepke or Ski could also explain the merits of bypass filtration, how widely it's used in boats etc. I understand long haul trucks usually have these installed.

NTA855 Cummins.
Oil was clear when I last dropped it
Has 150 hours on it now and still clear.

Lepke said:

I Many small diesels come with short spin on filters, but a longer version is usually available. Going to the longer size cuts the flow rate almost in half and catches more debris.

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I am installing a remote oil filter to my Kubota based genset
This will allow not only easy change but fitment of much larger filters
Oil has always been instantly black after change so it'll be interesting to see what results I get with a bigger filter.

1984 Perkins 6.3544 NA. Still transparent at 200 hours. It takes about 50 hours and a good light to see the level on the dipstick. The Perkins uses Rotella T5 10W30. My old Westerbeke gen would be black at 40-50 hours with same 10W30. New Phasor gen still transparent at first 50 hour change but darker than the Perkins at 200. No clue what the factory put in the Phasor. 1st oil change was with Rotella T5 10W30. Using NAPA Gold filters on all.

Lepke said:

I run clean oil. I centrifuge the oil every 25-50 hours. Before the centrifuge I used add on bypass filters. I've been experimenting with running clean oil since the 1960s and my experience shows much longer engine life. Maybe more than double if you're not running high exhaust gas temperatures.
With filtering, the slower oil passes thru a filter, the more dirt it traps. That why many Detroit Diesels have transparent oil longer. Older DDs had a bypass filter and no full flow filter. Later they had dual full flow filters that slowed the flow. Many small diesels come with short spin on filters, but a longer version is usually available. Going to the longer size cuts the flow rate almost in half and catches more debris.
Fine soot eventually clumps into larger particles along with other debris and gets to a size where it causes engine wear before a full flow filter can capture the dirt.
I haven't actually changed oil for more than 5 years, just add make up oil and test 1-2 times a year. The centrifuge also removes water.

Click to expand...

Doesn't oil also accumulate acidic combustion byproduct (other than soot) that makes it damageable beyond a certain concentration?

L

I use a Gulf coast bypass filter on my Cummins 6bt .

Filter element is nothing more than a large size bounty paper towel roll.


Change the filter every 100 hrs & add about a gallon of make up oil

I do a full oil change at 7-800 hrs.

Oil is tested every year.

The oil color stays almost clear which I understand is lack of soot

I

Lou_tribal said:

Doesn't oil also accumulate acidic combustion byproduct (other than soot) that makes it damageable beyond a certain concentration?

L

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I agree, Lou.

Besides soot, there are many factors which will limit oil life.
Increased acidity, decreased alkalinity reserve (TBN), changes in viscosity, oxidization, moisture or diesel contamination, silicon contamination, etc.

High oil acidity can be particularly damaging on engines that sit for extended periods without running.

Soot is more visible than the other issues, but I'd be more concerned about the things you can't see.

Ken E. said:

Cummins 6bt's.....The oil is pretty black after 10 hours of running them easy. Ironically, I've had 2-cycle Detroits that didn't turn black until 50 hours or so.

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50 hours on my 6bts since oil change and its still clean

When I DIY change it with a pissy little pump, it gets dirty quickly. When the mechanic does it with his vacuum sucker which he leaves connected overnight,the fresh oil stays nice and clean.

My Cummins 6bt 200 HP in my Dodge pickup stays clear on the stick till oil change (100 hours 5,000 miles). It only burns 2.5 GPH at hiway cruise. The Cummins 6ct 300 HP in my charter boat turns black on the stick at 15 hours. It burns 12 gallons an hour. I change the oil at 50 hours. It uses no oil between 0 and 50 hours. At 75 hours it's burning a quart every 6 hours. At 100 hours it's burning 2 quarts every 6 hours. I don't fully understand why it starts using oil after 50 hours. So I just change it at 50 hours. To put things in perspective, oil and filter runs about $100. 12 gallons per hour for 50 hours will be about $1,500 to $1,800 this summer. So oil changes are cheap by comparison.

Regarding additional oil filters and refining your used motor oil, I feel oil and filters are relatively cheap and am happy paying for new oil each time.

Ted

Our perkins stay clear for a little while, maybe 20 hours? but by the 100 hour mark when we change it, its jet black. There's no oil consumption and the annual analysis have all come back happy.

I'd be wary of a centrifuge system because I want the oil additives to be cleaning. I believe in better living through chemistry, but there's snake oil to be wary of. ...what I'm saying is, is: I dunno

bshanafelt said:

I use a Gulf coast bypass filter on my Cummins 6bt .

Filter element is nothing more than a large size bounty paper towel roll.


Change the filter every 100 hrs & add about a gallon of make up oil

I do a full oil change at 7-800 hrs.

Oil is tested every year.

The oil color stays almost clear which I understand is lack of soot

I

Click to expand...

A long time between changes but if the test says its good I guess it is.

I'll be interested to get our oil tested at 250 hours and see if we can double or triple the change interval, especially as for us its 40itres per change.

Ski in NC said:

Depends on the engine and the loading. Some 3208TA in high output apps you can change the oil three times in a row and it is black after a couple hours run. Run same engine at 1200 and it will stay clean for 20hrs.

Nothing wrong with black oil, it's just soot.

On my 450C, it is pretty black at 50-100hrs, I change it at about 300hrs.

If it bothers you, take a sample and see what the soot/insolubles are.

Click to expand...

What makes oil black? .. soot. What makes soot black? Cabon .. I think. And I’ve been led to belive that carbon is an abrasive and assume an abrasive will cause engine wear. Black engine oil is the norm though and our engines last a very long time (almost all) even including fairly significant negligence.

How much wear? Could be fly stuff or significant. I don’t see why we should be very concerned about engine wear. Very few here have repowered due to engine wear. Most all repowers are probably a result of negligence or just plain mistakes. And I suspect any fairly good maintenance proceedure re oil changes (and related practices) will allow our engines to last as long as we need them.

There’s a lot of unjustified worry about engine life here on TF IMO and probably all or almost all of it is a waste of time and money. However it’s probably certain that centrifuging or by-pass filtering does extend engine life I personally don’t think it will be enough to change your life.

But it makes much more interesting conversation than “what did you pay for your bow thruster”.

I too would be interested in a separate thread on centrifuges, from those who have them and know about them, please. I will start it now.

My CAT C7s turn the oil black very quickly after a full service (and that service happens every 200 hours or 12 months, whichever comes first).

I once read a thread from a trawler charter company in the USA, NW Explorations, where the Director said he installed oil centrifuges on most of the charter fleet and subsequently saw significantly prolonged engine life and much cleaner oil. I have been intrigued about engine oil centrifuges ever since.

Over here in Australia, my enquiries about oil centrifuges for engines of the C7 size (7 litre, in line 6, turbocharged) have met with a blank wall, so grateful for any thoughts.

Thanks,

H.

Do the c7 have a bypass filter Brishamish?

Has anyone worked out their oil change interval by using the chart method, which I assume all makes would have in their manual?

If I have worked ours out correctly, with the low rpm therefore low fuel burn we experience, red line, we don't even register on the scale so could extend ours from 250 hours to 600+ hours.

Hi Simi,

No, I don’t think my C7 engines have a bypass filter?

Hi, by the way. Have seen you out around at Peel and Sandhills. We Bert at RQYS. Pls come and say hello if you see us.

Hamish.

BrisHamish said:

Hi Simi,

No, I don’t think my C7 engines have a bypass filter?

Hi, by the way. Have seen you out around at Peel and Sandhills. We Bert at RQYS. Pls come and say hello if you see us.

Hamish.

Click to expand...

Shall do and same offer here.

Simi 60 said:

Has anyone worked out their oil change interval by using the chart method, which I assume all makes would have in their manual?

If I have worked ours out correctly, with the low rpm therefore low fuel burn we experience, red line, we don't even register on the scale so could extend ours from 250 hours to 600+ hours.

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What does the curved line represent? The 24 line is less restrictive than the 3 line.
What engines?

Have run 1960's DD 8-71 and newer 1995 DD Series 50 and with the std modern oil filter the oil is black on restart after a change.

Have a 6-71 built to WWII specks with a bypass filter , called color filter in that era, that is clean at 5 hours and just going light tan at 100-125 on change.

The black is called soot , but weather it is harmless or functions as fine grinding compound is unknown.

High Wire said:

What does the curved line represent? The 24 line is less restrictive than the 3 line.
What engines?

Click to expand...

Details here.

The graph above is for a NTA855M Cummins