Determining oil change intervals via analysis

I got an oil analysis done at Blackstone Labs just a few weeks ago. It
showed elevated levels of silicon. A third party analyst, Terry Dyson,
suggested that I had an air filtration problem, possibly that the air
filter was being bypassed. I pulled the air filter and found peanut
shells in the floor of the airbox. It turned out that a squirrel had
chewed a hole in the underside of the hose connecting the airbox to the
intake manifold. The hole was not visible to a casual inspection; I
needed a mirror to find it.

Had it not been for the oil analysis, I would have been feeding
unfiltered air and nut shells to the engine for the rest of its
(certainly shortened) life. It was worth the $30 to find this out.

 

More likely the gasoline or diesel propeller engines in smaller
aircraft (Cessna, etc).

They still use lead in gasoline aircraft engines, from what I hear...

Michael

 

Perhaps shortened, and perhaps never to be discovered. Equally - routine
air filter maintenance would have made the peanut shells apparent and likely
the resulting efforts to find the hole. At what cost? Likely, very little
to no cost with even an annual look at the filter.

However - in the context of the text quoted above - my comment was in direct
response to the assertion by jim beam that there was a reason to believe oil
analysis could predict engine failures which were likely to occur within six
months. Poppy cock.

Again though I will submit the question... What is your definition of
shortened? From 200,000 to 150,000 miles? To 75,000 miles? To 190,000
miles? What was the actual damage or effect on the engine from the shells
and the hole? Admittedly it could be significant over time, but that's not
guaranteed. Will it cause an imminent failure? I propose it will not.

 

The big value of doing an occassional oil analysis is to catch
mechanical problems when they are small and before more damage is done.

Case in point: Oil analysis caught the leak in the intake manifold of
our 2003 Olds Silhoette by detecting small amounts of anti-freeze in the
oil. This allowed us to get it fixed while the car was still under the
extended warranty and before bearing damage had been done.

$20 once per year for a "blood test" is well worth it IMO.


John

 

Oil analysis is no cure all, but can and does catch problems like fuel
dilution and anti-freeze contamination of motor oil.

Just because you have never used a tool and don't appreciate it doesn't
make you an expert .

John

 

I would have found it out without an oil analysis, because I replace
my air filters regularly. It's cheaper, and less ambiguous, than spending
money on an oil analysis and analyst.

 

Mike's dead on: a typical automotive engine lives and operates in it's
own world. Aircraft engines have theirs -which is different- and
racing engines have their own world.

Among other things, this means all those products you see advertised on
race cars may not have any value to your typical car. Example: Joe
Racer advertises some miracle engine treatment or some super motor oil
that helps him win, or ultra hype air filters. Maybe these things do
help him.

But when a race engine is getting torn down and rebuilt and/or replaced
after every race, there's no way to relate what he gets to what average
passenger car driver would get.

That ultra hype air filter might work great for 500 miles, and nobody
really cares if it fails because the engine is going to get rebuilt
anyway.

But put that same filter in a passenger car where it might go a year
between anyone even looking at it?

And what about oil? Suppose Joe Racer hypes a crappy brand. Who
cares. It only has to last A race. Your passenger oil needs to last a
lot longer under much more harsh conditions like stop and go, failure
to reach proper temps, jackrabbits, etc.

The message is use the right part for the right application, and that
goes for oil tests, lubricants, filters, fuel, tires, etc. Keep
apples with apples.

 

In my neck of the woods, air filters need to be replaced only once every
two years or so; they don't get dirty enough to warrant replacement
before then. I had replaced mine in Jan 2005 and wasn't due for a
replacement for another 8 months or so.

Perhaps there are some who pull their air filters every month just for
fun; I am not one of them.

 

Agreed John, but snipping my direct responses to direct statements made by
the OP and replying to a summation statement made in the context of my
complete thoughts does not serve your point well.

I do appreciate what an occasional analysis can do but I also appreciate
what other routine maintenance practices can do as well. My comments were
specifically in address of bold statements made by the OP in the text that
was included with my reply. I stand by those.

 

Well, perhaps you regard ignorance and stubborness as virtues, but I
don't. It never ceases to amaze me that people can look at scientific
data that refutes their beliefs and just dismiss it because they don't
like it. It takes all kinds, I guess...

 

Actually, it provides information that can be used for both. It
indicates if the oil is still functioning properly so that one can
adjust oil change intervals as necessary. Of course, you can choose not
to do so and in the case of aircraft, you may be legally bound to follow
a specific maintenance schedule. That's not true of privately-owned cars.

Wear always happens. The oil analysis will point to particular areas of
wear and indicate whether there is any abnormal wear that needs to be
addressed.

 

My question, and I don't know whether anything mentioned in the analysis
(e.g. active additive present in oil) actually addresses it, is whether
the oil has begun to leave deposits that could prevent proper oil flow
through the engine. The vast majority of failures I've seen have been do
to restricted oil passages, not the inability of the oil to lubricate.

 

While your other points are absolutely valid, I have to take issue with
this one. There are no "crappy" oils on the market, at least not as long
as you buy SAE certified oils (which most are). One can argue and
nit-pick and hypothesize that X brand is better than Y brand, but if
it's got the SAE certification on the label, it's good enough for any
car. About the only significant differnce in oils is between natural and
synthetic, with the latter being demonstrably superior in most test
criteria. However, the real-world difference is more in the realm of
"extra insurance" than "clear advantage", since natural oils are
certainly good enough. Perhaps the only clear advantage of synthetics
for normal driving is that you may get better fuel economy, especially
in cold weather.

 

I tend to agree. If an oil meets the certification criteria, it is probably
just fine. I have long felt that some oils tend to varnish the engines
a bit more than others, but this is a subjective and anecdotal comment.

Synthetic lubricants have some interesting test data, not all of which
apply to the primary job of lubrication. I am sure they are quite good,
and may use them in the future, but not to delay change schedules.

 

True, but during the warranty period it is the manufacturers that need
to be convinced. I'd change my Hyundai oil at 10K miles if I wasn't
worried about voiding the warranty. And with the 100K warranty, it
means I can't start my 10K intervals for a long time.


Matt

 

It is actually both. Yes, the main benefit for airplanes is avoiding
engine failure, but you can also extend drain intervals with oil
analysis. For large truck fleets, the analysis is typically all about
extending drain intervals.

Matt

 

I never used oil analysis when I owned my Skylane. I'm talking about
what others do.

Matt

 

It depends on what it indicates is wearing. Some things you can let go
for a while, and some you can't.

Yes, depending on the above.

GM doesn't make airplane engines.

If the oil was bloody, I'd really be worried.


Matt

 

With a car, sure I'd just keep on driving it. Oil analysis can't
predict with any certainty when an engine will fail. In a airplane, I'd
have it torn down and inspected. However, this is much easier than with
most cars. A good aircraft mechanic can rebuild the top end of an
airplane engine in the time the car mechanic is getting the accessories
removed from a modern car.


Matt

 

It is the sponsor's money that helps him win, not their product.

Matt