Get a hacksaw and cut the filter in half - it's not too hard, they are made
of pretty thin metal. Look closely at the internals and you should be able
to pick out some debris, unless your engine is really clean, not too new,
not too old, etc. A new engine will still be 'breaking in' and could have
more wear particles in the oil, whereas an old engine will be starting to
wear out and could have more wear particles in the oil. If you do a lot of
city driving, you will likely have dirty oil. If you drive 40k miles /yr
like I do, your oil will likely be quite clean if/when you change if by the
recommended schedule. Just stuff to keep in mind...
Just what are you hoping to see? The average OEM oil filter will remove
particles as small as 10 microns (maybe even a little smaller). A micron is
equal to 0.0000393700787", so 10 microns is equal to about 0.000394", or 4
/ 10,000ths of an inch. I guess if you have a microscope you could prove
that the smallest particles are being removed. If you can see any particles
with a visual inspection, you probably have problems.
I think the real question is, "what can get into my oil that needs to be
filtered out?" Cars don't use breather caps any more so we shouldn't have to
worry about unfiltered air with grit being pulled into the engine any more,
but oil changes and fills are not always done in clean room conditions. The
towel we wipe the dipstick with at the gas station isn't guaranteed free of
grit or dust. Okay, so maybe contamination is rare, but when it occurs we
sure don't want to pump abrasives into the close bearing surfaces of modern
engines. The amount of grit doesn't even have to be visible to be a big
On the original question, the filter size probably is determined by oil flow
and filter geometry, and those are changing. The filter in our Toyota has
(let's see if I can describe this) a half dozen lobes of pleated paper, so
the pleats are at a right angle to standard filter designs. If you think of
replacing the flat paper of each pleat in a normal filter with pleated
paper, you get the picture.
I thought there were folks who (1) changed the oil at x
miles, left the old filter in for x more miles, then
examined the oil; and (2) same thing, except the filter was
replaced after the first x miles. In (1), the oil was
Wear particles from the engine (anything that wears has to go
somewhere), slight amounts of blow-by by-products (the rings do not make
a 100% perfect seal) and by-products from the decomposition of the oil
A well maintained engine in it's mid-life stage probably leaves very
little in the oil filter, hence the small filter and every other oil
change replacement recommendation on modern Hondas. Indeed things have
changed a lot from the days when FL-1A size filters were the norm and
needed changing every 3,000 miles.
If you have a well equipped analytical laboratory handy then you are all
set to see what is really in your used filter. Otherwise, not much you
can do on the cheap.
There has to be a lot of "whatever" on the filter element.
Weigh a new filter. Now weigh a used filter, after you have drained the old
I may not be able to detect what actually is on the filter element, but it
has to be something that is not good to let through ?
That was going to be my suggestion. One could cut open a new oil filter,
remove the element and weigh it, soak it in clean oil, and then drain it
thoroughly. Now, take the used oil filter element and drain it. Weigh both
filter elements and compare the difference. To compensate for inherent
variability in the weights of the filter elements, it would be best to
repeat the process several times and use the mean of your measurements for
All you need is a lab quality scale to measure accurately and some
method to determine if the oil saturation changes with use.
Again, not a home project unless one has special equipment such as an
analytic quality scale.
One of your earlier posts suggests that you were comparing the clean dry
weight to the dirty oil soaked weight. This might lead to inconclusive
results. That's why I suggested using a clean wet weight for comparison. I
agree with the other posters that although it would be an interesting
academic exercise, time might be better utilized in just changing the filter
and forgetting about it. One thing to think about though is that
manufacturers include a high pressure bypass valve in their filters. This
valve diverts the oil flow in the filter bypassing the filtering element
when the back pressure is too high. This likely occurs when the oil is cold
and thick or when there's so much crud in the filtering element that it
starts impeding the oil flow through the element. Bypassing the element in
such cases at least prevents oil starvation in the engine.
This might lead to inconclusive results. That's why I suggested using a
clean wet weight for comparison.
OK, next time I change oil, I will do the "wet with oil" comparison.
To eliminate oil filter waste, I will just fill the new oil filter all the
way with new oil and then compare to the old one, all the way filled up with
Will report back.
It would be more accurate to thoroughly dry both elements (as in a low-temp
oven), then weigh them. There may be different levels of absorption you're
dealing with, not to mention the normal variance among filters to begin
The trapped particles are metallic (mostly iron). The
filter and the trapped particles can be washed and if
the filter is cellulosic everything can be ashed,
yielding metal oxides (iron oxide).
If the filter cannot be ashed (glass fiber filter) the
metal particles are dissolved in acid and then heated
to high temperatures, again yielding metal oxides (iron
If I were you, I would never change the oil or filter. It is a waste of
time and money.
Give it some time, and eventually your vehicle will start using oil, and at
some point, you will be changing the oil VERY often by just adding new oil!
Think of the time you will save draining the old oil and changing the
I smell an Infomercial there for a new Oil Reservoir like the washer tank.
Just push a button and add a qt. of oil to the motor!
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