TABLE OF CONTENTS Since a sample should be taken while the machine is running at some steady state, or shortly after shutdown, the resulting sample will be hot and any volatiles will be evident to the alert nose. Even after the sample is received in the lab, volatiles attack the nearest nose when the cap is removed. Fuel dilution, freon contamination, and other chemical contaminants can be clearly identified by the smell. Visually, you can also learn something, especially about the presence of water. Depending on the additives in the oil, water will sometimes quickly separate from the oil, so that you can see the water and oil separately if the sample bottle is clear plastic or glass. If the water forms a stable emulsion, the sample will appear milky or clouded.
Normally, wear particles and solid contaminants are not visible to the unaided eye they are simply too small. However, when severe wear is underway the metal wear particles are sometimes large and plentiful enough to form a glittering deposit at the bottom of the bottle. Again, with a clear bottle, you will be able to see these particles. This event would be indicative of an ongoing severe failure mode.
With regard to feeling the oil by rubbing it between the fingers, the particles would have to be quite large (and therefore severe) to be felt. While using your common "senses" can be useful in detecting abnormal oil conditions, keep in mind that...
