June 22nd 2009 Too Cheap to Buy Oil Analysis? Get it Free
It is best to rely on oil analysis to establish your oil change interval. However, on passenger car vehicles that only have a sump capacity of 4 to 6 quarts, 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.
Of course, the result is that most folks won’t pay for a “true” oil analysis - but they might be willing to perform their own “oil analysis”, if they knew how to do it. 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.
In the next few paragraphs you’ll find detailed instructions for one of six DIY oil analysis tests that you can use to establish the condition of your oil and whether it’s ready for a change.
Circles, Spots & Rings
There are a number of oil conditions that this DIY oil analysis test can help to reveal including products of oxidation, sludge, failure of your dispersancy additive package, water ingression, anti-freeze contamination, dilution from fuel contamination as well as high particulate levels.
While your engine (and the oil) is WARM (not HOT), pull your dipstick and place one drop of oil on a heavy, white, NON-glossy business card. In order for the oil drop to dry properly, you’ll need to place the card somewhere that it will be lying flat, but suspended in the air (so that the oil drop area isn’t touching anything - top OR bottom). 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 could also set the card across the top of a coffee cup or similar cup or mug.
Make sure that the drop dries completely before trying to evaluate the appearance of the oil drop. The list of “oil spot features” below should be used to evaluate the condition of your oil once you see that the spot has dried completely.
- A uniformly light colored circle or slight yellowish outer ring = “good” oil.
- A dense, dark deposit area = Dispersancy failure
- A black, pasty area = Glycol (Anti-freeze) in your motor oil
- Center of circle dark with distinct outer ring = Severe oxidation
- A dark center with surrounding rings = Fuel in oil,Fuel dilution
Details of the blotter spot test can be found within: Fitch, J.C., “The Lubrication Field Test and Inspection Guide”, Noria Corporation 2000