One thing I've seen is people insist on using their own brand of oil and justify it by using oil analysis. This
gives them a reading of the metals and other substances present in the oil. Based on these amounts, they draw conclusions
about the effectiveness of the oil they were using.
That's an inaccurate use of the data, and here's why:
SpectroGraphic Oil Analysis Program (SOAP for short, the most common test) takes a sample of your engine's oil and
burns in under controlled conditions. They record the spectrum of the light (the color of the flame, for those of you
who slept through physics class) and those colors tell them which metals and other substances are present in the oil and in
what amounts. Then a report is made of what metals were found and in what quantities.
Note that the oil is burnt to get the test results. There's nothing in a SOAP test that measures viscosity,
lubrication (friction reduction) quality, amount of additives left: no test is done to determine the quality of the oil.
It only tests for foreign materials.
While this may seem to indicate the quality of the oil, the next question is what amounts of metal is normal? No
two engine wear alike, due to how hard they're used, in what sort of envirionment they operated in, etc. And if you
forget and change the oil for a month, the amount of metal in the oil is going to go up simply because there's been more wear.
So there's no fixed number that indicates excessive wear.
Since every engine is unique, every engine has to set it's own "normal numbers" and is where the normal procedures for
SOAP tests come in. These are to change the oil as regularly as possible, usually after 100 hours of operation time
for airplanes. A sample of each oil change is sent to the SOAP testers. They send back the results that you
record. Over many oil changes, an average amount of metal can be determined. If, at a later date, a metal content
spikes up, then you know that something made of that metal is wearing more quickly than before and might be getting ready
to break. It's then up to the mechanic to determine which part that might be, which then suggests how much work it might
be to fix it. In short, SOAP tests are a analytic tool used to judge the health of an engine. Note that without
a meaningful average, there's no way to tell what's normal and what's not.
Notice that in none of these tests do the quality of the oil come into play. That is a completely different
set of tests done by the oil companies. Just because you're analyzing the oil, doesn't mean you're getting results about
the oil's quality. In this case, you're measuring the engine for wear indirectly by measuring the amounts of metal
in the oil, not the oil for it's quality.
In short, you can't justify second-guessing the manufacturer about proper oil simply by using SOAP tests. SOAP
data isn't valid for oil quality and, therefore, decisions about oil quality based on that data are meaningless.
HA! See why I can't post this on a bulletin board? Thanks for reading. See you next time.
