IL ANALYSIS IS REALLY THE BEST WAY to determine what your oil
change frequencies should really be. However, on passenger car
vehicles that only have a sump capacity of 4 to 6 quarts, and on
motorcycles and ATV's, it often can be cost prohibitive, since an
entire oil change (even synthetic) wouldn't cost all that much more
than a complete oil analysis.
So, for some, the best thing is to perform a "Poor Man's Oil
Analysis". It won't give you readings as accurate and precise as
results from a lab, but it can give you a fairly good idea of
how well your oil is holding up.
1. The Blotter Spot Test
This test reveals oxidation products, sludge formation,
dispersancy failure, glycol contamination, water contamination,
fuel dilution, and high levels of particles.
You want to place a drop or two of used oil on the surface of
chromatography paper (good heavy white card stock works pretty
well too). Lay the paper or business card flat, but so that all
but the very edges of the paper is suspended. For a fairly stiff
business card, placing two pencils down on a table and laying
the business card so that the ends are resting on the pencils
would work well.
You want to wait for the paper or card to absorb the oil drop(s)
which might take awhile. Once all of the oil has been drawn into
the pores of the paper you can begin evaluating the condition of
- A colorless spot or slight yellow outer ring - "good" oil.
- A dense, dark deposit zone - Dispersancy failure
- A black, pasty zone - Glycol (Antifreeze) in your oil
- A dark center with distinct outer ring - Severely oxidized oil
- A dark center with surrounding rings - Fuel in oil
Information for the blotter spot test can be found in:
Fitch, J.C., "The Lubrication Field Test and Inspection Guide"
Noria Corporation 2000
2. The Crackle Test
This test is useful for establishing water ingression into your
oil from condensation problems. Typically, you'll be most
susceptible to water in your oil if you are a short trip driver
and/or if your vehicle sits for long periods without being run.
If you have fuel in your oil, this can cause some disruption of
the test, so do the blotter spot test first to see if you have
any fuel dilution. If so, that is already a problem, so the
crackle test is a moot point.
To perform the crackle test, you place a very small quantity of
oil onto a hotplate of some sort which is set to a temperature
high enough to boil off any water in the oil. Since most oil
isn't volatile until it gets up around 375 degrees F or higher
(synthetics much higher than that), you could set the plate to a
temp anywhere between 250 and 350 degrees most likely.
At that temp, when you place the oil on the plate, you'll hear a
crackle as the water boils off. Should occur very quickly as
long as the amount of oil you use is small.
If there is no crackling, then you know there is no water
present. An oil analysis is more precise in that it will tell
you if the level of water in the oil is a problem and what that
level is, but the crackle test is a good cheap way to establish
3. Used Filter Inspection
This is pretty simple. Cut your filter apart and see what's in
there. If you see large amounts of metal shavings, some of which
seem fairly large, you may have some serious wear issues.
Also, if you have sludge problems, often you'll see the remnants
of it within the filter media as little "blobs" of "gummy" oil.
4. Oil on Water
Simple test. New oil will bead up when dropped onto the surface
of the water. Just a drop and you'll see. Either there is a
little drop of oil that maintains its integrity or the oil drop
spreads over the surface.
If the oil drop spreads, the oil is likely overly contaminated
5. The "Rub" Test
Shortly after a drive (but long enough after that your oil isn't
so hot it will burn you), take a drop of oil from your dipstick
and rub it between your fingers. If the oil feels particularly
"grainy", it is pretty contaminated and should be changed.
6. The "Smell" Test
Smell the oil. First, get out a bottle of new oil of the brand
and type you used for your last oil change. Smell it so you know
what it should smell like in good condition.
Then, take a few drops of oil from your dipstick and put it on
your finger or on/in some other medium. Smell it. If it smells
"burnt" in comparison to the new oil, you may be in need of a
change, oxidation has occured.
Now, understand, some oxidation is natural, and the presence of
oxidation itself is not necessarily an indicator that an
immediate change is necessary. It just means that your oil is
not in as good of condition as it was when it came out of the
The same is true of many of the tests above. Only oil analysis
can truly give a quantification of the problems listed above so
that you can truly know how "bad" your oil actually is. But, the
"tests" above are a pretty good way to get a decent idea of
whether your oil is OK for continued use or whether you should
at least CONSIDER changing it out.