The best way to establish realistic oil change intervals is via oil analysis. Of course, on small vehicles which require only 4 or 5 quarts of oil, the cost of the oil analysis is nearly as much as a complete oil change.nnOf course, the result is that most folks won’t pay for a “true” oil analysis – but they might be willing to perform a simple oil analysis themselves, if they knew how it could be done. It won’t give you readings as accurate and precise as results from a lab, but it can give you enough information to determine whether you should be changing your oil or not (as long as you don’t push things too far).nnIn 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.nnIt would likely also be in your best interests to learn a bit more about motor oil and filtration in general. You might find the following sites useful in this quest.nn- No More Oil Changes – Over 150 pages of motor oil informationnn- The Motor Oil Evaluator – nn- A Motor Oil Forum for discussion of motor oilsnnThe Spot TestnnUsing this DIY oil analysis test can reveal a number of potential oil problems that might lead to the necessity for draining of the oil: excessive particulates, condensation build-up, glycol contamination, fuel dilution, failure of dispersant additives, formation of sludge and oxidation products.nnWhile your oil is WARM (not HOT), pull your dipstick and deposit a single drop of oil on a heavy, white, NON-glossy business card. Put your white paper/card someplace so that it sits suspended and horizontal and in such a way that the oil drop area won’t touch anything – on the top OR bottom of the card. As an example, if you’re using stiff card stock or a stiff business card (which you really should be) you could set it across the top of a coffee cup.nnYou’ll want to be patient and wait for the paper or card to absorb the oil drop completely 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 your oil.nn- A colorless circle or somewhat yellowish outer ring = “good” oil.nn- A dense, dark deposit zone = Dispersant additive failurenn- A black, pasty area = Anti-freeze in your engine oilnn- Center of circle dark with distinct outside ring = Severely oxidized oilnn- Center of circle dark with outer rings = Fuel in oil,Fuel dilutionnnInformation for this business card test in: Fitch, J.C., “The Lubrication Field Test and Inspection Guide”, Noria Corporation 2000