On Aug 19, 6:33 am, "Jim Carter" wrote:
From those that use it, I'm interested in the usefulness of starting an
oil analysis program on a big bore Continental that already has 850 SMOH
and 450 STOH on an 1100 TBO. Does it take so long to establish a
baseline and trend that it would be better to wait until OH or can an
individual engine be compared to the class as a whole?


Anyone that says oil analysis is anything other than a trending
device, should be ignored. It is difficult to say how many samples
you need to establish a trend. It depends a lot on flying habits,
weather, environmental factors, oil, consistency of operation. During
summer months, where higher operating temps are to be expected, the
analysis may show different results. Likewise, cold winter months may
too show variation. You may even observe slight variance from sample
to sample. The larger the sample base, the better off you'll be to
determine variance. From what I've read, in some cases, statistical
analysis is required to truly separate the sample to sample variance
from the actual noteworthy deviation.

Of course, the above is ignoring serious problems which can show
themselves prior to catastrophic component failure.

Oil analysis has little down side and is an excellent tool to detect
early problems. Just don't expect a couple of samples to necessarily
establish a reliable baseline; then again, I guess it depends on the
margin of error you're willing to accept too.