It is best to rely on oil analysis to establish your oil change interval. Of course, on many passenger car vehicles that only take 4-6 quarts of oil, the price of the oil analysis is nearly as much as a full oil change.
Of course, the result is that the vast majority of vehicle owners choose not to pay for professional oil analysis services – 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 enough information to determine whether you should be changing your oil or not (as long as you don’t push things too far).
As you read this article you’ll find detailed instructions for 1 of 6 DIY oil analysis tests which could be used to figure out how your oil is performing and whether it’s ready for a change. In this way you can begin to set realistic oil change intervals for your vehicle.
It would likely also be in your best interests to learn a bit more regarding lubricants and filters in general. You might find the following sites useful in this quest.
- No More Oil Changes – Tons of motor oil information
- A Motor Oil Forum for discussion of motor oils
The Business Card Test
Putting this simple test into practice can expose a wide range of potential oil problems that might necessitate draining of the oil: build-up of condensation, contamination with anti-freeze, high particulate levels, dispersant additive deterioration, fuel in your oil, products of oxidation and sludge build-up.
You want to place a drop of used oil on the surface of chromatography paper (good heavy white card stock works pretty well too) . It’s important to be certain the oil is still warm but not hot. Place your white paper/card suspended horizontally above a table or countertop and so that the oil drop area will be touching nothing – on either side of the card. For instance, if you’re using stiff card stock or a stiff business card (which you really should be) you could lay two pencils down on a table (parallel to each other) and set the card with each end sitting on one of the pencils.
You’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 should be able to begin evaluating the condition of your oil.
- A colorless circle or slight yellowish outer ring = “good” oil.
- A dense, dark deposit zone = Dispersant additive failure
- A black, pasty area = 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
Information for the blotter spot test in: Fitch, J.C., “The Lubrication Field Test and Inspection Guide”, Noria Corporation 2000
Are you looking for more information regarding do it yourself oil analysis testing, how you can compare and contrast motor oils, how synthetics CAN and sometimes CANNOT be good options, how to compare the efficiency of various oil filters and much more? Click this link to my Motor Oil Bible Blog or take a look at the Motor Oil Bible ebook.