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Friday, September 22, 2023

Doug's Domain

Doug Vetter, ATP/CFI

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Monday, March 15, 2010

Oil Analysis Reveals Lead Wear Trend

(Image: Blackstone Labs Oil Analysis report from March 3, 2010)As you may recall, my previous oil analysis identified a slight rise in lead from an average of 4 PPM to 7. As the lab technician then indicated, and I agreed, that change did not warrant concern because it wasn't that far from the statistical average.

Yesterday I received the results of the sample taken last week and unfortunately it shows that lead has more than doubled to 18 PPM. The change has been identified by the lab technician as the likely start of a trend of increased bearing wear. The lab technician remarks that iron has also increased but that's only relative to the most recent samples. There seems to be some variability in the levels of iron over the previous five samples and the highest of 8PPM was found over 20K miles ago. As a result, I do not see iron at 10 PPM to be statistically significant.

I must admit that I am somewhat more skeptical of this sample than I would otherwise be because of the nearly 40% longer sampling interval. Some of the increase may very well be related to the increased time in service. The lab technician recommends additional changes with a shorter time in service and I plan to do that. I'm inclined to "reduce" the interval to 4500 miles so I can get the sample amounts back to a baseline to better identify the rate of change. However, doing the next change at 3000 miles would also serve to indicate the slope of the trend -- if the numbers are equal to or greater than this sample given half the time in service it might indicate the need to pull the engine sooner rather than later.

To better analyze the results and, I'll admit, do some daydreaming about what good could come of an engine rebuild I called Jim, owner of Metric Mechanic. He was kind enough to spend the better part of an hour over lunch this morning discussing the issue with me. I'll try to summarize it with a few points:

Of course, this is nothing more than the official start of the analysis and I intend to continue to use the vehicle without reservation. I'll likely schedule the next oil service and analysis in 3000 miles which translates into 2-3 months given my current driving habits. Stay tuned!

Mileage: 189777, Labor: $22