Post by Rick Sanders on Dec 3, 2007 13:31:42 GMT -3
The centre spot indicates the presence of sediment such as dust, wear particles, carbon, insolubles, and other contaminants. Depending on the combustion of the engine and the age of the oil, a corresponding sediment spot will form. If the oil is in poor condition and has not been changed the inner circle will probably cover most of the test. A healthy engine will show easily visible circles. If you have a very dark inner circle, and you oil has not been changed, we suggest you change your oil and filter, and re-test your engine.
