Mobil 1 5W30, 10980 kms, GMC Sierra 4.3l

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This time, I extended the OCI past my normal interval. You can see three previous analysis results, with the intervals listed. The Iron, Lead and Silicone readings are higher than it should be if you extrapolate from the previous results.

As an example, consider the Iron reading of 21 ppm. The Dec 13 analysis has 13 ppm on a 9270 km interval. Extrapolating gives 10980/9270 x 13 = 15.4 ppm.

Do the current results indicate that the OCI was over extended? I expected the Mobil 1 oil to handle the extended interval, even though I went about 10 % past the OLM on my truck. I was using a Mobil 1 oil filter. My oxidation, sulfation and nitration readings are also high when compared to previous readings.
 

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Lead shot up badly, w/o a drastic increase in Silicon or fuel dilution....not great.

Was during the winter, and we had a very cold winter this year, only thing I can think would cause this.

Did it see a lot of short trips and restarts in the cold?
 
10.9k kms shouldn't be too high for a quality oil. What kind of use did your truck see during this interval, lots of short tripping or hauling/towing?
 
I would not be concerned but winter conditions are the hardest on the oil. If you are going to extend your oil change interval, do it in the summer. My car produces more wear particles per mile in the winter vs summer.
 
I would run another interval at the same distance, take a sample, and see what lead reads then. Hopefully, it's just a streak.
 
Not excessive short tripping but a lot of stop and go driving because I live in the middle of a very busy city. My city/hwy miles ratio is about 80/20. The driving conditions were the same for the previous samples too.
 
This UOA does show some concerns, but too few samples to really understand the trending. Could just have been a particle streak; wont' know until the next UOA comes in. The Si is unlikely the issue; there are two other readings essentially as high and not correlation to metals. Without correlation there can be no causation.

Is not the 4.3L based on the "old" GM 350 engine (essentially 3/4 of the engine with two cylinders lopped off)? That old 350 engine was never a good wearing product; shed a lot of metals, historically. (I'm not saying it didn't run well or last a long time; it just has high wear-rates).
 
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Yes, the 4.3 is a three quarter 350 engine.
Si readings were very high initially on this engine. The first analysis had Si readings of around 80 ppm. That had me worried and I tried another air filter with no improvement in the Si readings. Wear metals figures were normal and not high. The Si figures has been slowly trending down over the years and at about the eight year mark in the life of the truck, Si figures finally dropped down to reasonable levels. My best guess is that the Si came from factory applied RTV somewhere in the engine.
 
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