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Sludge, Varnish, Soot & Ash

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This PDF is a brief explanation of the ASTM Sequence VG Engine Test. 


Motor oils with then SAE SL/SM/SN/SN+ must past this test to get the certification. This test run 216 HOURS. Keep that in mind. 


Also note that this test was meant to simulate 'low temperature operations" aka 'normal' service. Over heat it and all bets are off. 


Time for the punch line. HOURS. The oil is not required to meet any of these standards past 216 HOURS in service. 


Guess what your hour meter is good for? 😉 


As you can see this test is a bit more complicated than the simple 'oil inlet screen' result AMSOIL focuses on alone. 


Peppers life time miles/hours over 150,000 miles is a hair over 42 mph and at the maximum of 216 hours this has a mileage cap on it of 9,216 miles. I change at 5K. 


According to Syn-Lube the industry average miles/hours is 33 mph or 7,128 miles. Does that look familiar to you? Pretty standard 7,500 OCI by OLM these days. Regardless of oil capacity. The link below will show in pictures what an oil passing this test looks like on the inside: 




Question is.....are you AVERAGE? That is, does your speed AVERAGE 32 mph or more? Do you tow, pull, haul...let it idle for hours and YES those hours count. 

Second question is for you who like to do extended changes based on UAO what test are you reading that quantifies how clean the MOTOR is? Not the same thing as how clean the oil is. 

Edited by Grumpy Bear
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180 hour test. A shorter test with slightly lower deposit lobbied for by Ford and approved for SN/SN+SP service classes. 


Interesting note: In the fine print of page 3 footnote 5 of this PDF




See it?


If API CI-4, CJ-4, CK-4 and/or FA-4 categories precede the “S” category and there is no API Certification Mark, the Sequence VH (ASTM D8256), or VG (ASTM D6593), Ball Rust (ASTM D6557), and Gelation Index (ASTM D5133) tests are not required. 


Where did the 3,000 OCI come from? The 15 mph urban miles/hours average and the fact that the number of vehicles operating in actual 'normal' conditions is almost ZERO. Not a bad rule to follow for most folks. 

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lubricants-03-00054 (1).pdf


2.1. Engine Oil Samples Fully synthetic (Shell Advance Ultra, 10W-40) and semi-synthetic (Shell Advance AX7, 10W-40) engine oils were procured from Shell, and used as received. These two oils are used in four stroke motorcycle engines, and are known to have good lubrication, shear stability and ageing resistance [22].


You want a deep inside look at a commercially available oil right down the to hydrocarbons it is made from and degrades to? If you make it to page 70 the fun begins. (page 16 of the PDF). 


You will notice that at 120 C these oils will reach the entire 216 hour ASTM VG/VH test sequence time with little ill effect. Translated this is 248 F BUT not 248 F bulk oil temperature but rather 248 F absolute temperature or the highest heat it will see anywhere in the motor. So how hot is that? Pooling temperatures run 30 to 40 F higher than the cooling water temperatures. Pooling means exactly what it says. Anywhere oil pools in the motor. Lifter valley. Cylinder head rocker area and so on. In your run of the mill Ecotec3 motor with it's 207 F thermostat that throttles closer to 210 - 215 F pooling temperature could be as high as 255F! 


From Machinery Lubrication:


Piston Ring-pack Deposits and Movement

Piston ring-pack deposits can sharply reduce ring movement and flexing. Likewise, ring movement can greatly influence where deposits form and the lubricant motion (transport) within the ring-pack.

This ring motion defines the residence time of the lubricant in the ring-pack, which in turn affects the rate of lubricant degradation and where deposits will form (see Figure 2). Ring-pack temperatures can range from 195-340 degrees C.

Collectively, these conditions can accelerate piston-ring-liner (PRL) wear, impair combustion efficiency, increase blow-by and reduce oil economy (more oil consumption).

One way this happens is through carbon jacking. In this phenomenon, carbon buildup occurs in the ring grooves (fed by soot and oil degradation products). The corresponding ring movement restriction increases wear, blow-by and oil consumption with the rhythm of the piston.

Figure 2. The sequence of piston ring-pack deposit formation

Cylinder Wall Oil Evaporation

As much as 17 percent of total oil consumption is associated with liner wall evaporation. The more distorted (out-of-round) and rough (surface finish) the cylinder liner, the more oil film that will remain on the liner after the power stroke. High liner surface temperatures (80-300 degrees C) will cause a loss of this oil by misting and evaporation. Light oil molecules are more prone to evaporation. These light molecules are the first to deplete, and as a result, there is less evaporative loss toward the end of the lubricant’s service interval.

Not all oils of the same viscosity are equal from the standpoint of volatility (risk of evaporative loss). Some lubricants may exhibit as much as a 50-percent greater loss from volatility than others. This is influenced by the base oil’s molecular weight distribution.

Of course, temperature plays a key role. A low liner temperature translates to a low evaporation rate. Liner temperature is influenced by load, combustion efficiency and cooling. Approximately 74 percent of vaporization occurs during intake and compression strokes (no speed effects have been found).


We have a balancing act and the OEM's are stepping on the balance beam. 





From the same source: 


There is a range where both optimum performance as well as minimal wear share similar characteristics. That number lies in the 175-180 degree range as shown by the overlap in the chart which correspondingly requires a 180 degree thermostat. FWIW, higher operating temperatures of today's engines are to fight combustion by-products and pollution.


Porsche puts maximum engine life oil temperatures (bulk) between 180 - 210 F. 


So where are we. Water temperatures between 175 and 180 F will give pooling temperatures of 205 F and 250 F or on the path of lowest oxidation, sludge and varnish production. 


Problem is GM is running 207 F thermostats that hold closer to 212 F leaving pooling temperatures over 248 F shortening oil and motor life. I'll give GM this. Actual pooling temps in the Ecotec3 is a bit lower due to cold side oil cooler/heater arrangements. 


Now I don't know if you noticed in the opening PDF the composition of the Shell Synthetic but it was a single hydrocarbon meaning a PAO. Kind of important as it represents the best case in this discussion. 


Fact is this entire post IS best case! No consideration has been given to towing, short tripping which produces low miles per oil aging hours. This means the best oil under the best conditions based on this chemistry and industry average operating hours would be 200 hours * 33 mph = 6,600 miles OCI. 


IF you are using a PAO.

IF your water temperature is 175 - 180 F.

IF your pooling temperatures do not exceed 40 F over water temperature.

IF your bulk oil temperatures run 180 to 210 F. 

IF you are a long haul driver that doesn't tow, race, rat.

IF....That is allot of IF's.


Go back to the first PDF and go to page 18 pf the PDF (page 72 of the doc.). Note the effect of temperature on anti-wear additives. Primary among them ZDDP. And what is the secondary feature of ZDDP? It is you PRIMARY antioxidant. When you running hard with an OEM thermostat you can use up 30 to 35% of the additive package in as little as 24 oil hours. 


So...what does average look like for you truck? How hot is you coolant and oil? What are your miles/hour numbers? What oil chemistry are you using? How well do you filter? How sharp is your tune?


Parting thought. The Sequence VG/VH test have a maximum deposit limit. To leave a deposit at all it has to oxidize. To oxidize it must be, in that location, depleted of antioxidant additives and attacking the base oils chemistry. The newest VH test no longer has a specification for 'grade and report' for 'ring sticking'. They know they have stepped off a cliff with their hands tied by the EPA. SO???? Make an HONEST assessment of you situation. Monitor and think then:










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How many times have you heard this:


Temperature A general rule for oxidation is that the operating life of the lubricant will be reduced by up to 50% for every 10°C (18°F) increase above 85°C (185°F).   (akn: BVAvanced)


I expect most people take this to mean for "mineral oils".  I know I did for a very long time. Thing is, it is true of ALL base oil types! The key is in the phrase "Operating life of THE lubricant". Different base oil types have different 'Operational Life Times" under the same conditions but they all follow the 50%/10C rule. 


That lifetime depends on its makeup. How the molecule is constructed. We've been over that a hundred times. Point is, a base that is twice as resistant to oxidation will last twice as long but will oxidize following the same 50%/10C rule. That is as long as oxidation and heat are the only factors...and they never are. 


But here is the takeaway. The difference between the oxidation 'life times' between a Conventional oil and the very best Group IV/V blends is only slightly more than double. 





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  • Grumpy Bear changed the title to Sludge, Varnish, Soot & Ash


A bit of light reading



Original Paper

Open Access

Published: 17 June 2016

Corrosive–Abrasive Wear Induced by Soot in Boundary Lubrication Regime

F. Motamen Salehi, D. N. Khaemba, A. Morina & A. Neville 






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A bit of light reading Redux 


Did you go blind? Head swimming? Quit before the Grand Finale? Tire of the double speak and pages of telling what isn't instead of what is? Join the club. This is bathroom material for a fact. Let's see if I can Cliff Notes this for ya. 


SAE paper 2019-01-0301 is the reference for this next statement. Soot accumulates at a rate of 1% soot per 15,000 Km (9,300 miles). IN WELL TUNED MOTORS. Gives context not noted in this paper. 


First note is this test used concentrations in 1% increments to 8%.  So there is no useful data for 0.333% to be shared in these documents unless you dead set on very long OCI's OR you motor is in a poor state of tune that manufactures soot at a greater rate than 'average'. 


Second note. Keeping a good sharp tune is key in maintaining the lowest soot production possible. 


Third note: At soot rate levels expected during the 'severe' schedule oil change interval of 3,000 miles soot induced phosphate inhibiting is a non factor. http://www.hastingsfilter.com/Literature/TSB/94-1R1.pdf  (reference for severe OCI length from API and filter manufactures)


Fourth note: I don't care how old that linked document is as is witnessed by this soot study.


Fifth note: This test was intended to study the mechanism of wear and found to be corrosive/abrasive and not three body abrasive. That means the ZDDP zinc layer is absorbed by the soot and metal to metal contact made as if no ZDDP were present. Can it happen? Sure...this study shows that. It also shows that it isn't as likely as one may think. Soot concentration is to low and a blender using the CORRECT ZDDP/Dispersant package won't have an issue with this in 'normal' concentrations seen in real world operations with reasonable OCI's.  


Sixth note: Buried in this report is an odd fact worth noting. 12,000 rpm centrifuge did NOT remove all soot held in suspension from filtered samples AS INDICATED BY THE CONTIUENCE OF THE BLACK COLOR. Why does that matter?


You don't change oil because it 'wears out'. Oil doesn't wear out. But it does things much worse. 


1.) Soot concentration. It eventually loads to a harmful point. 

2.) Becomes contaminated by water to the point of saturation. 

3.) Becomes fuel contaminated to the point of viscosity losses that are unacceptable

4.) Thermal or free radical oxidation or nitration to a point of saturation where in it creates sludge and varnish

5.) Becomes saturated with insoluble materials. 


And finally additive depletion. Additives will hold off oxidation, corrosion, hinder foam, suspend solids so that they may be filtered or removed via a good old fashion oil change. That is until they are used up. Additives extend the useful life of oils but they still have a useful life and it isn't always dependent on the additives being depleted or the base oils being used. 


Sometimes a change in warranted by reaching some other point of saturation additives have no command over and the base oil has a limit for.  



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How Severe Is Your Service?




Ever play chess? The end game is the result of the actions and/or inactions of every piece on the board. Motor oil advertising likes to focus on one pieces moves that that particular chemistry defends or attacks best. As they are all quite similar the group focus become unified and no one stands out. In the end it seems that oil's greatest enemy is thermal oxidation followed very closely by extreme load wear protection. These two even have something in common. The kind of conditions one might expect like towing or racing, Is that how we drive? 


This study done in 2011:  

https://www.bts.gov/archive/publications/highlights_of_the_2001_national_household_travel_survey/section_02#:~:text=On a daily basis%2C the,about 23 vehicle miles traveled.


[Quote] On a daily basis, the average person traveled 40 miles, most of it (35 miles) in a personal vehicle. Because more than one person can travel in a personal vehicle, these 35 person miles amounted to about 23 vehicle miles traveled. [End Quote]


So the one way average trip, likely to work, is 11.5 miles. Did you read the first link concerning oil sump temperatures?


[Quote] Nitration of the oil from NOx in the blow-by gases that enter the sump increases at lower oil sump temperatures, i.e., below 80 degrees C (175 degrees F), and increases as sump temperatures approach 70 degrees C (160 degrees F). [End quote]


For Joe Average the sump temperature never reaches  a stable temperature that hinders nitration. Oil temperature lags water temperature by 2X to 3X in distance or time and what nitration that does happen in colder sumps is not reversed once the heat gets above 175 F. For such short tips the oil will not get to 150 F. Log it then tell me I'm wrong. I do 😉 


It would be wise to stop thinking in terms of 'oil oxidation' and start thinking in terms of "oil DEGRADATION".  And you may have noticed that the list of things that degrade oil is ever growing. Not that these chess pieces are new but rather they are coming to into focus. 


Thermal Oxidation, Free Radical Oxidation, Nitration, Soot Levels, Water Dilution, Fuel Dilution, Additive depletion, VIM polymer permanent shear. This is a long list and I expect still incomplete.


Increased wear is what happens AFTER the oil is damaged, degraded. Yes assuming sufficient minimum viscosity has been met. Let's not pick nits here. 


PREDICTIVE analysis takes note of the results in wear metals but sees them BEFORE they wreck havoc in patterns and events in the used oil itself. It concentrates on the oil first. Kind of what a UOA is suppose to be...


Go back to the first link and you see that many items that cause nitration are caused by or accelerated by either the physical condition of the motor OR it's state of tune


Anyone that has read my drivel for very long knows I am no fanboy of UOA's. And yet I just spent this entire post hinting that looking at the products of oil degradation could be, okay, ARE, the best tool in your 'Oil Maintenance" tool kit! So...what's the disconnect? 


The reports these UOA's deliver and the test run and test methods used to get those results. That's my issue. A "Feel Good" report generated from low grade or incomplete testing not only isn't helpful...it's misleading. It's worse than driving in the rearview mirror. So let me clarify; I'm not a fan of useless incomplete low grade testing resulting in a feel good report whose primary purpose is collecting you money. 


But I digress. Harping on 'Reactive" UOA's is another topic.


Getting you to look at what severe service is and that for most people SEVERE SERVICE is their daily commute is. 



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  • 5 weeks later...



The left most column is the element detected. Header labeled Kirkland is the 'average" production result. The far right column the result of the UOA. Results are in ppm. 


The yellow column is a calculation for TRIAX S7. I'm going to get some blow back on this and that is fine. And it will center around accuracy. Lets work on that. The ratio of this blend was 5:1 and yes I'm ignoring the 8 ounces of makeup oil used straight during the OCI this sample came from and the 6.5% fuel load (10.4 ounces) It's a 5 quart system. I want to show the uncomplicated version and I'll worry about perfection later. 


Here's the math. The result for the base oil calcium is 1350. We multiply that by 5 (the ratio). We multiple the UOA result by 6, the the total parts of the ratio. 5+1. Then subtract the later from the former and you have the concentration of this element in the TRIAX S7. 


http://www.pqiamerica.com/calcium.htm#:~:text=Calcium is typically related to,commonly used in engine oils.&text=It is also important to,with a high ash content.


TRIAX cautions not to blend higher than 5:1. The link above explains why? Ash formation


Here's the thing. The test ...it's....elemental..... Think on that a minute. Remember your chemistry? No matter what reactions occur 'within the oil' the number of calcium atoms remains the same. Ditto every other element in the periodic table. Yes, even those the participate ON the metal do so in a state of equilibrium. Zinc etc. And yes there is some concentration possible and dilution possible. Fuel? Water? NOACK burn off some causes for each. 


Calcium and magnesium are the two most common detergents and calcium is being replaced more and more with magnesium to battle LSPI. 


Although detergents are multifunctional, that is act as part of other systems such as corrosion protection and anti wear, oxidation inhibitors...they are primarily detergents. Detergents clean. 


As simple as that may sound it isn't. Not all calcium or magnesium compounds are equal in effectiveness. 


https://www.stle.org/images/pdf/STLE_ORG/AM2016 Presentations/Synthetics_Hydraulics/STLE2016_Synthetics and Hydraulics III_Session 3L_J. Wei_Performance of High TBN Sulficylates.pdf


Have fun unraveling that ball of yarn!













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  • 3 weeks later...

I posted in another thread recently about rotary bomb (ASTM D2272) testing differences between different base oils. 


Synfluid and Mineral Oils


As much as I write about OCI lengths somehow it seems that marketing continues to trump the facts. 




Even  FAQ's are full of stacked cherry picked data and product specific reference mismatches. You have to read each word carefully. Consider it's context. Understand the tests application to YOUR WOLRD. 


As jaded as this will make you do not miss the lessons. Start to train yourself to think in terms of directionalities. This one is a perfect example. Brand X oil 'CLAIMS' that you can safely triple you OCI. What is the reference for such a claim? Look at the graph. It's a Group II base. Critical thinking. You manual says Dexos1 Gen 2. You look up a dozen oils you are looking at and see that the SDS shows the base oils to be HYDROCRACKED, not hydrotreated which when coupled with a search for the CAS number shows that oils meeting that spec are Group III oils....🤔


If you take the marketing at face value you triple the 7,500 mile OCI and guess what? 22,500 miles! Pretty close to a 20K boast, eh? 


Have you ever seen a TBN/TAN comparison of Mobil 1 ESP at 25K? 5K TBN/TAN near equal. 7200 miles upside down. 

Mobil claims this stuff is good 'on the bottle' for up to 20K miles. However in the fine print in the limited warranty it states this:




What the period of coverage is

The Mobil 1 limited warranty is valid for 10,000 miles or your vehicle’s OEM recommended oil change interval, whichever is longer.

Additional requirements for all Mobil 1 products include:

  • Oils must be put in service not later than five (5) years from the date of purchase; and
  • an oil change must be completed every twelve (12) months.



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Do UOA's include a test for how dirty the oil is? How much junk, carbon etc. is in the oil?

Seems the tests are more for evaluating OCI's by tracking how much the oil has broken down. What about how much junk is in the oil and being recirculated through the engine. 

Removing dirty oil was a big factor for me doing 3K OCI's.

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3 hours ago, diyer2 said:

Do UOA's include a test for how dirty the oil is? How much junk, carbon etc. is in the oil?

Seems the tests are more for evaluating OCI's by tracking how much the oil has broken down. What about how much junk is in the oil and being recirculated through the engine. 

Removing dirty oil was a big factor for me doing 3K OCI's.


I expect @customboss will have some thoughts on this. Boy I hope so.....



The things that make oil 'dirty' are cared for by the base oils solvency and the additive packages construct.


There are things that can be keep in solution. A base oils solvency. 

Things that are kept in suspension. The dispersant package.

Things that keep it filtered. 

Things that can be neutralized. Detergent package. 

Things that can be terminated or hindered. Antioxidant package. 

Things that can be protected chemically. Corrosion inhibitors and EP adds ZDDP etc. 


Depending on the case a chemistry is in place to either stop or slow a reaction that will 'eventually' be used up. 

A chemistry to neutralize a reaction that will eventually be used up. 

Disperse the debris until the chemistry is use up. 


All in all not much of anything happens that generates a large amount of debris until the chemistry is used up or the solvent becomes saturated. IN A WELL TUNED MOTOR.  


Here's the thing however. No matter how good the add package is...it is NOT perfect and never will be. When you read about an oils ability to keep your motor clean it has a POINT OF REFERNCE. And ASTM test and an SAE limit. 


Which means?


Even before the package is used up there are deposits building up in that motor that are deemed acceptable. Those deposits are CUMLATIVE. Well most are than are harmful. Varnish i.e.


The last tool in the kit is the OCI. The solution to pollution is dilution. That is what an OCI does. Yes it also restores additive levels. 


The question most not asked is...

"Are you protecting your oil or your motor" 


I kid you not. You can keep a motor alive and well just as long with a shorter OCI and 'basic chemistry" as you can a killer oil and longer OCI's. Yes yes provided the basic chemistry is suitable for wear and you choose the right viscosity. 


See that is the problem. The information we get is from someone else's requirement for your motor. 


When you take in information you have to ask yourself 'How does the information I'm being feed make that person money"?


When a lube shop says 3K miles and sells an oil that goes easy 5K?

When an OEM stays 7.5K to 10K but UOA says it's done by 5K? 

When a boutique sells 20K to infinity OCI's for oils costing 3 to 20X?  


Remember the data they use to sell with is the data they want you see and not all the data and often time sans relevant points of reference.


Has your system failed you? YOU are doing fine.






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7 hours ago, diyer2 said:

Do UOA's include a test for how dirty the oil is? How much junk, carbon etc. is in the oil?

Seems the tests are more for evaluating OCI's by tracking how much the oil has broken down. What about how much junk is in the oil and being recirculated through the engine. 

Removing dirty oil was a big factor for me doing 3K OCI's.

diyer2 great question and Grumpy Bear did a good job of starting out to explain it.  


Blackstone uses one test I throughly recommend pentane insolubles.  Particles and deposits that are insoluble will be riding the engine oil hopefully and not sticking to the inside of the engine. ANY insoluble reading above 0.1 % in modern engines is too high. 


When I was active in my business we used FTIR readings specifically soot to get a grip on " dirtiness of oil".   The % of soot should below the level of detection in a healthy engine via FTIR so 0/ ZERO/ZED is the target. 


The break down of the oil tells a story too but you'd have to be a tribologist to understand the reactions and levels to look for because they vary for each individual engine family and type related back to that chemistry. 


Dispersants carry "dirt" to the oil filter via polarity however new fuels and the fact our engines are DI,VVT,EGR, and PCV will impact that polarity and ability of the dispersants to carry the " dirt ".  In other words if the oil filter can't trap it because it's not suspended its probably attached to your ring lands, oil galleries, or PCV plumbing making deposits. 


The deposits that can't be dispersed will have to be solubilized some way as Grumpy indicated and hopefully be mechanically drawn to oil filter or at least re-burned by EGR function. 




Engine oil should have less than 0.5% fuels in oil volume, the limits mentioned above for soot or insolubles. 


Less than 500 ppm of water via Karl Fischer titration.  Do NOT rely on crackle tests. 


Viscosity still in grade desired. 


Wear control below max for that engine design. 


TBN high enough to counter acidic response, TAN low enough we aren't having out of control acids eating soft metals or making shellac/varnish. 


Additives still having ACTIVE phosphoric activity via Anti-Wear reading in FTIR.  PPM levels via ICP don't tell you how active the additives are. 


Good base oils that solve all that out. 


Hope that helps but it's not simple in reality.  







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[quote] The pitch was that formulators could potentially gain the same anti-wear or friction-reducing effects with less additive if they replaced some base fluid with alkylated naphthalenes. [end quote from above link]


Every once in awhile I run across something like the above than just puts a pit in my stomach. Bold underline is mine in the above quote. ExxonMobil is a big player in this market and while they spout the advantages of this or that they never tell you if what they are promoting is actually in the product you are buying. Not many do. 


 Inuendo? Oil is one of the few things we buy that is sold such. :wtf: 

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Spot on Grumpy Bear,. 


Marketing isn't science and scientists and engineers don't pull the trigger on what management and marketing decide to share with the consumer. 


A balanced formulation can me made for each application but how many people know that? 


Blanket bench testing and viscosity grade read across will make a perfect lubricant for say a Ford carbon packing Ecoboost fall apart in a AFM/DFM 6.2L GM V8 eat its lifters. 


Appropriate application of chemistry is key.  How many consumers care?  Few because for 100 years we've been told advertising is truth....pigs to slaughter really. Sad. 


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