The most comprehensive method for establishing feasible oil-change interims is through oil analysis. This, in general, can turn out to be quite heavy on the pocket as a proper professional analysis can set you back as high an amount as the cost of the changing of 5 quart of petroleum-oil.
Thus for most people, the more suitable option is to do a home test. This test might not be as perfect as the professional one or even remotely as informative. However it will be able to give you a decent approximation of how your motor oil is faring.
The following paragraphs will guide you through one of the six do it yourself oil analysis tests which you can perform at home to check the condition of your oil and see if there is any need of changing it.
Test using a Business Card
This method can give you a variety of break down symptoms of the oil that might indicate the need to change your oil: building up of condensation, excessive particulates, contamination of the glycol, dilution of fuel, forming of sludge and other oxidation products, failure of the dispersant additives. Put a drop of the sample oil onto a strip of chromatography paper (heavy white business cards can work). Be certain that the oil is warm (not hot). Put the paper such that it lies suspended and parallel to the grounds surface so that the oil drop isn’t in contact with anything. For example if the paper is stiff, you can set the paper on 2 pencils lying parallel to each other on a flat surface. Leave the apparatus untouched till the drop loses its moistness. Follow the checklist below to grade your oil:
- If a pale, yellowish ring forms around the dried up drop — The oil is good.
- If there is a thick, dark deposit area — There’s a failure of dispersant additives.
- If there is a Black, past like area — There is Glycol or anti freeze in your engine.
- If the dry oil drop has a dark circle with outline at the centre — Oil is drastically oxidized.
- If there is a dark center with concentric rings surrounding it — Fuel is diluted
Info on “Blotting Test” in : “The Lubrication Field Test and Inspection Guide” by Fitch, J.C., Noria Corp. 2000.