Cat C7...2 UOAs on same oil...???

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Originally Posted By: mikeshauling
Ok i just got my first UOA back from Caterpillar. What do these #s mean??? 11,000 on truck 6,000 on the oil. Rotella15-40 ...2009 CTD 6.7 my 2nd oil change on the truck, 1st UOA. They didnt give me a TBN ? I am running an AMSOIL air filter since @ 500 miles too. Good or bad report here ??


The above is the lead-in from mikeshauling's thread ...and I hope he doesn't mind me borrowing his Caterpillar UOA format and numbers ...I've got two UOAs from Caterpillar on my C7 to discuss so I just used his format and typed in my numbers to the right of the ones for his 2009 CTD 6.7.

I'm a fulltime RVer and in Dec 2007 I bought a used 2005 Freightliner with a 300 hp Cat C7 that had 10K miles on its odometer ...and it still had the original oil from its April 2004 build date! When I got the truck back to the RV park there was a mobile lube guy there who seemed to know his stuff ...so I immediately had the oil changed using a Cat filter and 7 gals of Rotella 15w-40 from 1 gal jugs.

The lube guy didn't have any sampling kits on hand ...so I drained some of the used oil through a white tee shirt and inspected it with a magnifying glass ...everything seemed ok and the engine ran fine ...then later I learned that my S/N included a batch of heads with potential casting issues involving pin hole leaks of oil-to coolant, fuel-to-coolant, fuel-to-oil, and coolant-to-oil ...so at 2K I went to the Cat shop in Las Vegas and they took an oil sample from the dip stick using a pump ...and a coolant sample from the radiator petcock ...and the Cat lab said both samples were in spec!

After 4K of cross country towing at 33K GCW ...and 1 qt of added oil ...I had the oil changed at 6K by a Cat shop in Springfield, MO and another UOA/coolant sample done ...so except for the added qt both of these UOAs are from the same 7 gals of Rotella 15w-40! Everything checked ok again ...and I've had 2 more oil changes w/o UOAs and I now have 28K on the engine.

After finding this site I want to learn all about UOA and engine wear mechanisms ...because at age 68 this truck will probably be my last so I need it to outlive me! So here's some questions about my UOAs ...why did sodium decrease and the additives molybdenum, calcium, magnesium, zinc, and phosphorus increase? I suppose the decrease in viscosity is normal for a HEUI engine? The 6K UOA also had a listing for PFC=1.59 ...but there was no explanation as to what that is?

Since I've always got a free plug right next to the truck ...and nothing better to do with my time ...I routinely run the coolant/oil pan heater for 45-90 min before starting up ...is there any down-side to preheating the oil 3 to 4 times a week ...which is about how often I use the truck?

I've been using Rotella 15w-40 ...and changing it about every 6K or 6 months ...I've considered switching to synthetic Rotella 5w-40 ...because I tow in the SW during the summer and supposedly synthetic is better in hotter weather ...but several Cat dealers have advised me against using it and said I'll probably develop oil leaks if I do ...so far I haven't dripped a drop of any type of fluid ...knock on wood! Any comments or advice on how to keep my C7 running for as long as possible will be appreciated!

...............CTD 6.7L.....C7 7.2L
(ppm)..............6K........2K...6K
copper----------12...........7.....9
iron--------------64..........8...11
chromium-------1...........0.....1
aluminum-------5...........1.....1
lead--------------1...........0.....0
tin-----------------0..........0.....0
silicon----------10...........6.....8
sodium----------7..........14....2..?
potassium----16............8....6
molybdenum---5...........3...11..?
nickel------------0.........0.....0
calcium-----2262.....1847..2293..?
magnesium--103........41...60..?
zinc-------------124....1033..1396..?
phosphorus--1042.....899..1258..?
(count/ml)
soot-------------6...........0.......3
oxidation-----20..........16.....17
nitrate-----------7..........6.......7
sulfation------21..........21.....20
water-----------N...........0......N
antifreeze-----N............N......N
fuel--------------N............0......N
viscosity------13..........13.9..12.2
PFC...............?...........?...1.59..?
 
Hi,
CAT recommend the following viscosities for the C7 against the ambient range noted;

15W-40 mineral - (12F to 50F)
5W-40 synthetic - (-22F to 50F)

I prefer a 5W-40 synthetic lubricant when combined with an ELF series Donaldson Synteq filter. This ensures a rapid full flow of lubricant during the critical warm up/start up periods
Any lubricant used IMO should be one that is endorsed as acceptable by CAT!

Sadly CAT engines (especially the C12,15 and etc) do not have a very good reputation today!!

Only similar engine families can be compared and even then individual engines within the family will have variances due to operation, driving style, fuel quality and etc

The soot level of 3% would be very close to the maximaum allowed for the engine/lubricant. It is an unsually high figure IMO for such a low mileage

PFC may refer to a solvent - as a Perflourocarbon - it needs more explanation in a UOA but can be safely disregarded in your context

Your UOAs are a good starting point for "trending" that will enable you to keep a finger on the lubricant's health and certain aspects of the engine's condition. This will enable you to reach a cost effectice OCI
 
I analyzed my UOA "ppm Iron" readings ...and below are 4 graphs which are mostly "self explanatory" ...if anyone's interested in more details I'll present and explain the equations and assumptions that were used to generate these graphs ...because analyzing diesel engines is my retirement hobby!

http://ernesteugene.com/FTE4/C7a.jpg
http://ernesteugene.com/FTE4/C7a1.jpg
http://ernesteugene.com/FTE4/C7ad.jpg
http://ernesteugene.com/FTE4/C7ad1.jpg

Here's an overview of my approach ...the mass of Iron entering the engine's oil supply is generated by wear on the cylinder walls ...and this wear increases the cylinder Bores by a given amount for each 50-mile interval traveled ...the solid red "0% Filtered ppm" curves give the "ppm Iron" readings if there's no "oil filtration" at all ...and the solid blue "5% Filtered ppm" curves give the "ppm Iron" readings if the multiple passes through the oil filter for each 50-mile interval traveled remove 5% of the Iron mass from the crankcase oil.

The first two graphs are for a "constant wear rate" equal to a Bore increase of 0.001" per 100K miles traveled ...but this gives a predicted "ppm Iron" reading at 2K miles that's higher than the measured value! The second two graphs are for a "dual wear rate" which accounts for running empty during the first 2K miles ...and then towing for about 60% of the following 4K miles ...and that gives a perfect fit to my measured UOA "ppm Iron" readings!

The conclusions I draw from my graphs are ...my Cat "high efficiency" oil filter is only removing "5% of the Iron mass" from the crankcase oil for each 50-mile interval traveled ...but after about 6K miles this "5% rate of removal" is sufficient for a steady-state "ppm Iron" reading to be obtained ...which means by 6K miles my oil is sufficiently "contaminated with Iron" to allow a "5% removal rate" by the oil filter to eliminate the Iron at the same rate at which it's entering the crankcase oil ...if I extended my OCI to 10K miles ...instead of changing my oil at 6K miles ...my engine would experience more wear during that last 4K miles prior to an oil change than it does during the first 4K miles following an oil change ...and that would needlessly wear my engine at a faster rate!

I'm currently researching the area of "abrasive wear" ...which is somewhat like a "nuclear chain reaction" ...because if even one particle gets in between two sliding surfaces ...that particle generates several more particles ...and those particles grind off some more particles etc ...and the only way to stop this "chain reaction" is to change the oil ...and more frequent OCIs will increase the "life expectancy" of any engine ...especially a HEUI engine!

I'm sure everyone is familiar with the concept of "dog years" ...but the link below gives a graph for associating an equivalent "human age" with the "mileage age" of a 7.3L Power Stroke ...and this graph basically applies to any diesel engine with a comparable displacement.

http://ernesteugene.com/FTE2/LifeCurves.jpg

A detailed explanation of these "human age" plots can be found here... http://www.ford-trucks.com/forums/922342-life-expectancy-curves-human-vs-stock-7-3l.html .
 
Ernest,

keep in mind that the results on a UAO are not to be taken as exact measurements. You can easily see a 3-4 ppm difference in the results of the same oil sample run through the analysis twice. IIRC the test is reading the 4-7 micron range.

I do not know why Molybdenum would show up on your UOA report unless you had some engine work done and some the the parts were coated with a factory lube that contained Molybdenum.

Sodium dropped, this is a good thing. Was some engine work done on the truck before or when you purchased it? Could be some residual, but the value is dropping so the trend is heading in a positive direction.

The viscosity did drop down to a 30 weight on your 2nd UOA but it did not affect your wear metal values. Did you notice any drop in oil pressure?

Glad to cross paths with you again Ernest!

Rich from FTE
 
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Originally Posted By: White_Buffalo
Ernest,

keep in mind that the results on a UAO are not to be taken as exact measurements. You can easily see a 3-4 ppm difference in the results of the same oil sample run through the analysis twice. IIRC the test is reading the 4-7 micron range. Glad to cross paths with you again Ernest!

Rich from FTE


Nice to see you again too ...and I'll address all your comments eventually ...but first just to make sure everyone understands what I'm doing ...here's an outline of how I did the wear-rate analysis using my ppm Iron readings...

This equation gives the progressive increase in the engine's total SCV=Swept Cylinder Volume ft^3 due to each 50-mile interval of cylinder wall wear... WVC={(NC)(Pi/4)(S)(B2^2-B1^2)}/(1,728) ft^3 ...where WVC=Wear Volume of Cylinders ft^3, NC=Number of Cylinders, Pi=3.1416..., S=Stroke in, B=Bore in, and B1 and B2 are the Bore values at the beginning and end of each 50-mile interval traveled.

This equation gives the u-lbm (micro-lbm) mass of cast Iron that's "bored out" of the cylinders due to each 50-mile interval of cylinder wall wear... WMI={(WVC)(MDI)(10^6)} u-lbm ...where WMI=Wear Mass Iron u-lbm, MDI=Mass Density Iron lbm/ft^3, and for cast Iron MDI varies from 424.5 lbm/ft^3 to 486.9 lbm/ft^3 ...and I used the upper-range number of MDI=475 lbm/ft^3.

This equation gives the total mass of oil in the crankcase... COM={(COC)(MDO)} lbm ...where COM=Crankcase Oil Mass lbm, COC=Crankcase Oil Capacity gal, MDO=Mass Density Oil lbm/gal, and MDO={(SGO)(8.345)} ...where SGO=Specific Gravity Oil ...and I used SGO=0.84 which gives MDO=7.0 lbm/gal.

I used this quote from the Blackstone site ..."One of the limitations to oil analysis is that we can only tell you about the wear metals that we can see with the spectrometer, which are between about 1 and 15 microns in size."...to assume the u-lbm mass of Iron wear debris enters the lbm mass of crankcase oil as particles with diameters of 0.0006 in (15 microns) and smaller ...and that the "relative mass concentration" of these "micron size particles" in the "crankcase oil mass" are what's being measured by my UOA ppm Iron readings.

I calculate the mass of Iron wear at the end of each 50-mile interval ...and add that number to the previous value of Iron wear mass so as to obtain a running sum of the total Iron mass being worn from the cylinders... IMT=Iron Mass Total u-lbm ...and I also calculate the Iron mass being filtered out by the multiple passes through the "full-flow" oil filter for each 50-mile interval... IMF=Iron Mass in Filter u-lbm ...and then the "Iron mass" remaining in the "crankcase oil mass"... IMO=Iron Mass in Oil ...is given by... IMO=IMT-IMF u-lbm ...and finally I calculate the "predicted" ppm Iron readings from... ppm Iron={(IMO)/(COM)} u-lbm/lbm!

As indicated in the picture below the "crankcase oil mass" circulates through a "full-flow" filter and through a "bypass" filter ...and for the sake of using some numbers let's assume that for my 28 qt C7 each 50-mile interval traveled gives 10 passes through the "full-flow" filter and 1 pass through the "bypass" filter ...none of my current graphs include the "bypass" filter but future versions will because I'm interested in estimating how much improvement I might get if I install a bypass filter!

http://ernesteugene.com/FTE4/Crankcase.jpg

The "full-flow" oil filter can't actually filter "micron size particles" in the conventional sense of having small enough pores in its media to block them ...because the filter would plug-up and go into its bypass mode giving no oil filtration at all (this corresponds to the red curves in my graphs) ...but with each pass through the "full-flow" oil filter a few of the "micron size particles" do "stick" to the filter media and/or to larger size "debris" already on the filter media ...and if 0.5% stick for each pass then 5% of the Iron mass in the oil is filtered out over the course of each 50-mile interval ...and that assumption is used for the blue curves in my graphs.

I have 2 data points for ppm Iron ...8 ppm at 2K miles with no towing and 11 ppm at 6K miles with 60% towing during the 4K miles following the 8 ppm reading. I can adjust the parameters in my model so as to pass a "blue curve" through these "data points" in several different ways. In my graphs I chose a dual wear rate of 0.0008"/ 0.001" per 100K miles combined with a 5% Iron mass removal rate for each 50-mile interval traveled.

A higher wear rate combined with a higher flirtation efficiency ...or a lower wear rate combined with a lower flirtation efficiency are also possibilities ...but based on a report of bore wear on tear down ...I think I've about got the correct wear-rate assumption dialed into the model for my C7! I'm headed north to Jacksonville, FL soon and I'll stop by the local Cat shop there and see if they've measured some bores after tear downs at known mileages ...and I'd like to hear anyone's thoughts on this subject!

The ASTM D5185 test method covers the determination of additive elements, wear metals, and contaminants in used lubricating oils by inductively coupled plasma atomic emission spectrometry (ICP-AES) ...but they want $38 to download an 8-page document that covers this ...so far here's what I've come up with for free!

The table below gives some reported accuracies ...and multiplying the Standard Deviation given for Iron ppm by 3 implies my 2 data points for Iron ppm... 8 ppm and 11 ppm ...should have a "3-sigma" error of less than 1 ppm! I'm also analyzing my Silicon ppm ...and using the same 5% Silicon mass removal rate for each 50-mile interval traveled ...the results for my ppm Silicon data match the results I got using the Iron ppm data ...I'll get to the rest of your comments later because I've got to stop having fun and get back to my taxes as the wife wants to get them in the mail tomorrow!

http://ernesteugene.com/FTE4/Accuracy.jpg
 
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