It is wise to utilize professional oil analysis services in order to determine what your oil change intervals should really be. This can be cost prohibitive, though, since a professional oil analysis can often cost as much as a 5 quart petroleum 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 their own “oil analysis”, 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 will discover the complete details for performing one of six DIY oil analysis tests which can be used to establish the condition of your oil and whether it’s ready for a change.nnYou might also want to consider learning a bit more regarding oils and filters in general. You might find the following sites useful in this quest.nn- The Motor Oil Bible – Over 150 pages of motor oil informationnn- The Motor Oil Evaluator – motor oil comparison specificationsnn- A Motor Oil Forum for discussion of motor oilsnnThe Blotter Spot TestnnThe use of this simple layman’s oil analysis test can unveil a number of possible oil problems that might cause your engine to be in need of an oil change: excessive particulates, condensation build-up, glycol contamination, fuel dilution, failure of dispersant additives, formation of sludge and oxidation products.nnWhile your engine (and the oil) is WARM (not HOT), pull your dipstick and place one drop of motor oil on a heavy, white, NON-glossy business card. Place your white paper/card in a location where it will be suspended and parallel to the ground and so that your oil spot touches nothing – on the top OR bottom of the card. For instance, if using something relatively stiff you could place it across the top of a coffee cup.nnWait until the oil drop is no longer moist. Use the list below to evaluate the condition of your oil based on the DRY oil spot.nn- A colorless circle or slight yellowish outer ring = “good” oil.nn- A dense, dark deposit zone = Dispersant additive failurenn- A black, pasty zone = Glycol (Anti-freeze) in your engine oilnn- Center of circle dark with distinct outer ring = Severe oxidationnn- Center of circle dark with outer rings = Fuel in oil,Fuel dilutionnnDetails of this test procedure found in: Fitch, J.C., “The Lubrication Field Test and Inspection Guide”, Noria Corporation 2000