oil sample?

OK, that's pretty high mileage. The other wear metals look fantastic. The only concerns I would have would be the iron, silicon, and soot. I'm thinking your ok on the change interval, how long have you been on this maintenance schedule?

 

If you have an extention on your draft/blowby tube that puts it close to the ground, axle legnth or longer, you can suck dust and dirt into the enging with that, especially if the engine fan is on blowing dust everywhere while moving slow.

The engine will creat blowby pressure at idle or under load, but will usually create a vacuum when holding back. I learned that on my oil analysis. I always had high iron and silicon on my 12.7. New filters, every connection checked. The only thing I did different was extend the blowby tube to keep oil from getting on the axle.

 

I think your Iron is too high for only those few miles. Soot is slightly high as well. You using any additives?

 

I pulled the last 2 oil samples from my maint records for something to compare yours against. There was 20k miles on the oil from the first sample to the second sample. All elemental values in parts per million(ppm). some numbers are percentage, i will mark those as i go.
Cat C15 ACCERT with 980k miles , no engine work done as yet. Shell rotella 15w40 oil, no bypass system, fuel and oil filters changed at each oil change. Highway OTR work, I idle about 15 percent ( hot nights etc).

Sample 1 : There was 16k miles on the oil this sample related to.
Contamination; silicon 3.4, potassium 3.2, sodium 0, fuel (%) <2.0, glycol 0, water (%) <0.1, soot(%)0.3, sulfation(%) 96, nitration(%) 101

Oil condition; boron 164, barium 0, calcium 1560, magnesium 279, molybendum 50, sodium 0, phosphorus 941, sulfur 3327, zinc 1247, visc@ 100*C (cst) 14.2
oxidization (%) 95, BN(mg/KOH/g) 6.37. The TBN result indicated the oil was suitable for further service. I dropped that oil and changed it.

Wear metals; white metal 0, babbit 0, iron 16, nickle 0.3, chromium 0.8, titanium 0, copper 3.7, aluminium 2.3, tin 0.2, lead 1.7
Wear metal rates were considered normal.

Sample 2: There was 20k miles on the oil this sample relates to.
Contamination; silicon 3.4, potassium 2.9, sodium 0.9, fuel(%) <2.0, glycol 0, water (%) <0.1, soot (%) 0.2, sulfation(%) 69, nitration (%) 108

Oil condition; boron 18, barium 0, calcium 1161, magnesium 776, molybendum 34, sodium 0.9, phosphorus 960, sulfur 3462, zinc 1235, visc @ 100*C 15.4,
oxidization(%) 94, BN(mg/KOH/g) 8.09. The TBN result indicates the oil is suitable for further service. I dropped and changed the oil.

Wear metals; white metal Very light, babbit 0, iron 20, nickel 0.5, chromium 1.0, titanium 0, copper 4.8, aluminium 1.5, tin 0.2, lead 1.0.
Wear metal component rates were considered normal.

 

It can be hard to compare one sample to another. Alot depends on the way the sample was done. Mine are done by a lab called "Wear check", they do the sampling for customers of the "Kleen oil" bypass system. Yours were done by CAT so could be a different reporting system etc.
I look mostly at the fuel dilution, glycol and water,viscosity, soot and wear metal levels. The TBN test allways comes back saying the oil is suitable for further use but i dont take it past 20k miles even if the sample says it can be used longer.
I think once you get a few samples done around the same intervals you will see the pattern that your engine has.

 

Just a suggestion but you could put an hour meter on the engine. My father-in-law does all his services on the farm equipment and his trucks by the hour. He says its more accurate way to do services on machinery.