What wears Diesel Oil out?
- Thread starter ZZman
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the use of the engine!
Usually it is contamination. The high compression ratio creates blowby of fuel/combustion products past the rings into the oil sump. These tend to be acidic also.
Some well worn diesel engines actually "create" more oil in the sump this way and the dip stick will show over fill with time.
Some well worn diesel engines actually "create" more oil in the sump this way and the dip stick will show over fill with time.
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Oh, I forgot to add why diesel engines usually have such a large oil sump (other than they are physically larger) and another reason diesel engines are harder on oil. In gas engines, the top piston ring can expose the motor oil to temperatures of 320 °F. In diesel engines the top ring can expose the oil to temperatures over 600 °F. A larger oil capacity keeps the oil temperature down and the oil lasts longer.
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Some OTR engines NEVER change their oil-change the bypass filter, top off, & you're GTG. Some diesels that use an oil-powered injection pump (such as my 6.0 work van) shear oil quickly, some (like my Dodge Ram Cummins & 6.2 GMC) could go 25K easily with synthetic & a simple bypass to keep the soot levels down, & some leak & blowby so badly (like my 300D) that the oil practically changes itself & suffer from massive soot loading! All different.
Hi,
ZZman - In my experience over many years and millions of kms it has always been contaiminants - simply, the condemnation limits (the engine manufacturers' or Oil Cos') of soot or iron being reached. It always see-sawed between the two!
ZZman - In my experience over many years and millions of kms it has always been contaiminants - simply, the condemnation limits (the engine manufacturers' or Oil Cos') of soot or iron being reached. It always see-sawed between the two!
Doug, can you look at your PM's? cheers..steve
Hi,
BobFout - Yous said:
"I'm wondering if we're now going to see where TBN becomes the limiting factor and not soot or wear metals?"
I suspect it will depend on the engine families involved. I think the change to the rate of Adds (TBN structure) depletion may no longer be as "linear" as in the past
IME the TBN was always well in reserve in my case so it could have been lower as a VO component
In the past the starting TBN was an issue that related more to fuel types (high sulphur). It was a blance as in effect the higher the TBN the greater the undesirable SA levels. As you are aware high SA levels can quickly relate to high wear rates in some engine families
I suspect the new Adds will in the end equal about the same engine wear rates and the same or maybe better OCIs in many engine families - with the generally lower sulphur levels in fuel as the catalyst
Time will tell...........
sprintman - 'tis empty?
BobFout - Yous said:
"I'm wondering if we're now going to see where TBN becomes the limiting factor and not soot or wear metals?"
I suspect it will depend on the engine families involved. I think the change to the rate of Adds (TBN structure) depletion may no longer be as "linear" as in the past
IME the TBN was always well in reserve in my case so it could have been lower as a VO component
In the past the starting TBN was an issue that related more to fuel types (high sulphur). It was a blance as in effect the higher the TBN the greater the undesirable SA levels. As you are aware high SA levels can quickly relate to high wear rates in some engine families
I suspect the new Adds will in the end equal about the same engine wear rates and the same or maybe better OCIs in many engine families - with the generally lower sulphur levels in fuel as the catalyst
Time will tell...........
sprintman - 'tis empty?
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Originally Posted By: ZZman
You would think with the huge sumps you could stretch those OCI's out so something must be going on.
A Detroit Diesel DD15 with its' 47L sump, average speed 40mph, 50,000 mile OCI and average mpg of 6 has a specific stress on its' oil of ~2.8MW-hr/L.
An average passenger car that gets 25 mpg, av. speed 30 mph, 10000 mile OCI, 5L sump does ~0.8 MW-hr/L. MW-hr = megawatt-hr.
So the diesel's oil is worked 3.5 times harder. That would tend to break it down.
Incidentally, the OM364LA and OM441LA tests work the oil at >5 MW-hr/L. (SAE Technical Paper 2000-01-1986)
Charlie
You would think with the huge sumps you could stretch those OCI's out so something must be going on.
A Detroit Diesel DD15 with its' 47L sump, average speed 40mph, 50,000 mile OCI and average mpg of 6 has a specific stress on its' oil of ~2.8MW-hr/L.
An average passenger car that gets 25 mpg, av. speed 30 mph, 10000 mile OCI, 5L sump does ~0.8 MW-hr/L. MW-hr = megawatt-hr.
So the diesel's oil is worked 3.5 times harder. That would tend to break it down.
Incidentally, the OM364LA and OM441LA tests work the oil at >5 MW-hr/L. (SAE Technical Paper 2000-01-1986)
Charlie
Hi,
ZZman - Some lubricants handle soot much better than others and this is due to the Adds and the structure of the base oil
Soot tends to agglomerate and the dispersants (and other fluids, esters perhaps) in the lubricant's structure act to prevent this. Some additives may even "join up" with the increasing soot content
It is interesting to note that with Detroit Series 60s the max. allowed soot was 1.5% with CG lubricants but was 3% when using CH lubricants. So the lubricant's technology plays a very important role in soot management. Some Oil Companies will even condone up to 6-7% in certain applications
I have seen many severely soot contaminated internals caused simply by using the wrong lubricant - usually an "old" specification disallowed by the engine manufacturer
Due to the structure of the engine some are more tolerant of elevated soot levels than others. In my case my engines were operated up to 4% (sometimes higher) without a problem. The condemnation levels are usually around 3% for North American heavy high speed diesels
As to engine lubricant operating temperatures, these have been very well managed over some decades now - usually by intercoolers.
With Approved mineral 15W-40 lubricants Detroit Diesel for instance state that up to 110C as the "normal" lubricant operating temperature. First warning is given at 115C and engine shutdown occurs at 121C.
My normal average operating temperature was around 103C and the maximum recorded was 112C - using a fully synthetic 5W-40 lubricant
My average OCI was 90kkms (56k miles) and the viscoity of the lubricant at this point was always very close to the VO. Using a centrifuge may have helped in this regard
I think your OCI is (very) reasonable with a late series synthetic HDEO. A UOA at around 5k would confirm this
ZZman - Some lubricants handle soot much better than others and this is due to the Adds and the structure of the base oil
Soot tends to agglomerate and the dispersants (and other fluids, esters perhaps) in the lubricant's structure act to prevent this. Some additives may even "join up" with the increasing soot content
It is interesting to note that with Detroit Series 60s the max. allowed soot was 1.5% with CG lubricants but was 3% when using CH lubricants. So the lubricant's technology plays a very important role in soot management. Some Oil Companies will even condone up to 6-7% in certain applications
I have seen many severely soot contaminated internals caused simply by using the wrong lubricant - usually an "old" specification disallowed by the engine manufacturer
Due to the structure of the engine some are more tolerant of elevated soot levels than others. In my case my engines were operated up to 4% (sometimes higher) without a problem. The condemnation levels are usually around 3% for North American heavy high speed diesels
As to engine lubricant operating temperatures, these have been very well managed over some decades now - usually by intercoolers.
With Approved mineral 15W-40 lubricants Detroit Diesel for instance state that up to 110C as the "normal" lubricant operating temperature. First warning is given at 115C and engine shutdown occurs at 121C.
My normal average operating temperature was around 103C and the maximum recorded was 112C - using a fully synthetic 5W-40 lubricant
My average OCI was 90kkms (56k miles) and the viscoity of the lubricant at this point was always very close to the VO. Using a centrifuge may have helped in this regard
I think your OCI is (very) reasonable with a late series synthetic HDEO. A UOA at around 5k would confirm this
Doug: How would 1 um bypass filtration play into this discussion? I'm edging a little off topic here, but....?
Such a filter would catch a lot of the iron but begs the question whether high iron levels are cause or effect... e.g. is the iron primarily an indicator that the lubricant is breaking down or a cause of further wear. Logic dictates both, of course, but I wonder what the percentages of each would be.
I get conflicting information as to soot, which, unless it's agglomorated (to some degree indicating an worn out add pack), is mostly at sub-micron sized. No doubt such a filter would catch some soot, certainly the agglomorated material and larger particles as well as some smaller via scintering of the filter. I'm just trying to get a handle on how long a 1 um bypass filter can extend oil life against the ravages of soot?
Such a filter would catch a lot of the iron but begs the question whether high iron levels are cause or effect... e.g. is the iron primarily an indicator that the lubricant is breaking down or a cause of further wear. Logic dictates both, of course, but I wonder what the percentages of each would be.
I get conflicting information as to soot, which, unless it's agglomorated (to some degree indicating an worn out add pack), is mostly at sub-micron sized. No doubt such a filter would catch some soot, certainly the agglomorated material and larger particles as well as some smaller via scintering of the filter. I'm just trying to get a handle on how long a 1 um bypass filter can extend oil life against the ravages of soot?
Soot is a sign of incomplete combustion in a diesel-poor engine condition, fuel turned up too high, even a clogged air filter. Soot at high levels becomes an abrasive & clog piston rings & journals, bypass filtration helps remove it.
I found this and thought it was a good short read:
http://www.performanceoiltechnology.com/engine_soot.htm
http://www.performanceoiltechnology.com/engine_soot.htm
Hi,
Jim/ZZman - Soot is/was typically why By-Pass filters are used with diesel engines. Some will recall the large Luberfiners used on earthmoving equipment and trucks some years back - soot was the main reason!
Soot is the product of diesel engine combustion process and more or less by the quality of the fuel used (diesels are "oil burners" - you see this as a heavy diesel accellerates (espcially until tubo plays "catch up". Worse perhaps in pre-chamber engines, accerated via turbocargers, better when using MAN's "M" process and now much better with precise fuel delivery via ECMs but not assisted by using EGR. High injection pressures produce soot particles at smaller sizes. Soot forms agressive particles (agglomeration) that cause excessive wear and seperate out via centrifical forces etc to "soft" sludge up engines. This can eventually clog filters and retrict flow into the lubrication system
The diesel engines combustion process does increase the viscosity of the lubricant over time. This becomes an engine efficiency factor too. A 40% increase over VO is a typical condemnation point. As the oil becomes more contaminated it flows less readily through the ring pack (this can take up to five minutes) thereby increasing ring, piston and wall wear. This process also causes ring sticking and oil ring clogging at the extremes
Dispersants act to isolate the soot paticals (prevent agglomeration) but are consumed so the level of active dispersants is a decreasing number. Oil top up helps with maintaining the active dispersant level and mains viscosity! This is acknowledged in some engine designs. DD two cyled engines have a mx. soot allowed of 0.8% but oil topup is usually around 1ltr/1k kms in these engines
Typical FF filters are somewhat efficient down to 15micron (absolute or nominal - or so) and By-Pass filters are advertised at various levels of efficiency lower than that. Soot particals are much smaller than 15microns (perhaps a fifth of a micron or so) but these agglomerate to sizes in the order of 2-3 micron. This range is a high wear point in engine technologies where small clearances are involved and the lubricant "film" is very thin! Some engines have/had both FF and by-pass filters installed as standard
By-Pass oil filters typically have an oil flow at around 10% of pump output - some more, some less.
I always used a centrifuge on my engines. These are quite efficient to sub-micron levels and ideal for use on engines with high injection pressures. They tend to stabilse lubricant viscosity. My version had a compacted capacity of 0.6Ltr/g. The uptake rate was averaged at .0025g/km giving around 240kkms (150k miles) between each 10min clean out.
In this circumstance the FF filters (Donaldson Synteq) became redundant as they were always spotless when disected at OCI of 90kkms (56k miles). They were replaced with 30micron SS washable elements!
I believe this device was responsible for drastically reducing cam component wear rates!
Many cartidge type By-Pass filters are nominally rated at around 10microns. Some types are advertised at better than this but I suspect that flow then becomes an issue as does pressure drop in time! In some tests the rate of component wear (turbocharger spindle bearings) when comparing cartridge and centrifugal cleaning systems has shown an advantage of 40% in favour of the centrifuge
I cannot give exact figures that relate increasing soot levels to an increase in wear metals. I suspect in my experience that they are not related until around 4% soot level is reached. Then depending on the quality of the lubricant (ability to prevent further agglomeration) I suspect that the rate of Iron uptake in the lubricant will be directly related to any increase in soot levels. I suspect that this would far exceed the soot to Iron relationship to that point by as much as 10-30% depending on engine technology and lubricant quality
I hope this is of some interest
Jim/ZZman - Soot is/was typically why By-Pass filters are used with diesel engines. Some will recall the large Luberfiners used on earthmoving equipment and trucks some years back - soot was the main reason!
Soot is the product of diesel engine combustion process and more or less by the quality of the fuel used (diesels are "oil burners" - you see this as a heavy diesel accellerates (espcially until tubo plays "catch up". Worse perhaps in pre-chamber engines, accerated via turbocargers, better when using MAN's "M" process and now much better with precise fuel delivery via ECMs but not assisted by using EGR. High injection pressures produce soot particles at smaller sizes. Soot forms agressive particles (agglomeration) that cause excessive wear and seperate out via centrifical forces etc to "soft" sludge up engines. This can eventually clog filters and retrict flow into the lubrication system
The diesel engines combustion process does increase the viscosity of the lubricant over time. This becomes an engine efficiency factor too. A 40% increase over VO is a typical condemnation point. As the oil becomes more contaminated it flows less readily through the ring pack (this can take up to five minutes) thereby increasing ring, piston and wall wear. This process also causes ring sticking and oil ring clogging at the extremes
Dispersants act to isolate the soot paticals (prevent agglomeration) but are consumed so the level of active dispersants is a decreasing number. Oil top up helps with maintaining the active dispersant level and mains viscosity! This is acknowledged in some engine designs. DD two cyled engines have a mx. soot allowed of 0.8% but oil topup is usually around 1ltr/1k kms in these engines
Typical FF filters are somewhat efficient down to 15micron (absolute or nominal - or so) and By-Pass filters are advertised at various levels of efficiency lower than that. Soot particals are much smaller than 15microns (perhaps a fifth of a micron or so) but these agglomerate to sizes in the order of 2-3 micron. This range is a high wear point in engine technologies where small clearances are involved and the lubricant "film" is very thin! Some engines have/had both FF and by-pass filters installed as standard
By-Pass oil filters typically have an oil flow at around 10% of pump output - some more, some less.
I always used a centrifuge on my engines. These are quite efficient to sub-micron levels and ideal for use on engines with high injection pressures. They tend to stabilse lubricant viscosity. My version had a compacted capacity of 0.6Ltr/g. The uptake rate was averaged at .0025g/km giving around 240kkms (150k miles) between each 10min clean out.
In this circumstance the FF filters (Donaldson Synteq) became redundant as they were always spotless when disected at OCI of 90kkms (56k miles). They were replaced with 30micron SS washable elements!
I believe this device was responsible for drastically reducing cam component wear rates!
Many cartidge type By-Pass filters are nominally rated at around 10microns. Some types are advertised at better than this but I suspect that flow then becomes an issue as does pressure drop in time! In some tests the rate of component wear (turbocharger spindle bearings) when comparing cartridge and centrifugal cleaning systems has shown an advantage of 40% in favour of the centrifuge
I cannot give exact figures that relate increasing soot levels to an increase in wear metals. I suspect in my experience that they are not related until around 4% soot level is reached. Then depending on the quality of the lubricant (ability to prevent further agglomeration) I suspect that the rate of Iron uptake in the lubricant will be directly related to any increase in soot levels. I suspect that this would far exceed the soot to Iron relationship to that point by as much as 10-30% depending on engine technology and lubricant quality
I hope this is of some interest
Doug PM sent...s
what Doug says IMHO with new low sulfur fuels soot and wear metal are what cross over the condeming line first well add TBN also
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