One thing to keep in mind about oil analysis. Once you choose a lab, stay with them. There are several methods that labs can use to "count" wear metals, contaminates, and additives. In most cases it is not possible to get an EXACT part per million count. The different methods will give different "counts" when using the same sample of oil.
For example, you drain your oil at 10,000 mi, 20,000 mi, and 30,000 mi and take an 8 oz sample from each. You use the 8 oz of oil from each drain and use it to send a 4 oz sample to two different labs for testing.
Lab A posts iron wear as 15 ppm on the 10,000 mi sample, 18 ppm on the 20,000 mi sample and 16 on the 30,000 mi sample.
Lab B posts iron wear as 22 ppm on the 10,000 mi sample, 29 on the 20,000 mi sample, and 26 on the 30,000 mi sample.
You see different numbers on identical samples, which is correct? BOTH OF THEM! Now neither is going to be an exact count, but both are going to be close and the numbers will be consistant. Consistant meaning that if Lab A ran an Iron wear analysis on the same sample 10 times, it will get the same result each time.
What you are looking for are trends. If you are draining your oil every 10,000 mi and the wear and contaminate numbers are always similar and all of a sudden they change ,you know something caused it and you can study the rest of the test results to give you clues to what is causing the change.
For example, your Iron wear is always between 15 and 30 ppm, lead, tin, and copper are each between 2 and 15 ppm,and the sodium is always between 2 and 8 ppm and silicon is always between 8 and 15 ppm. Now, the last test shows iron at 35 ppm, lead at 78 ppm, tin at 57 ppm, copper at 81 ppm, sodium at 28 ppm and silicon at 11 ppm. What caused the higher wear? Clues are the near normal iron wear, but higher Lead, tin and copper wear, normal silicon ppm and high sodium ppm. Most engine bearings are made of tin, copper and lear and these metals are seldom used anywear else in engines. Sodium is present in most coolents and rarely in anything else. most coolents will attack tin, copper, and lead but have little effect on iron. So even if the analysis shows a NO to antifreeze and water contamination , you may still have a small coolent leak that is causing the added wear, but not enough to trip the antifreeze flag and the water is quickly been evaporated at the high engine temps so the water content in the sample is normal. This is the most likley cause.
Now, if you had been sending samples to several different labs you would not be getting consistant enough data to really know what is normal unless there is an extremly different change, which may be too late to rectify the problem.
The other key is to ALWAYS make SURE you are getting a representive sample that has not been contaminated with anything.
DO:
Use only the sample bottles supplied by the lab. If you use a petcock to get the sample keep it covered with a baloon or condom to keep it clean or carefully wash it and drain the first 10 oz or so into a can thad then draw the sample. Best is to use a pump made for this to draw a sample out from the dip stick tube, using a new tube each time. Sample only hot oil from a running or recently running engine.
Don't:
Take samples from the filters or from the container you drained the oil into. Keep your hands and anything from touching the sample.
Rember that a poor sample is just as bad as no sample at all.
I hope this helps.
Rudy
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