A complete record of oil analyses you've performed can prove to be a great tool when selling a piece of used equipment. It shows the potential buyers how you have maintained the equipment as well as any adjustments you made to it during its life. The history also is a good indicator of potential future repairs and overhaul requirements. When buying a piece of used equipment yourself, you also can take advantage of the benefits an oil analysis can offer. However, without knowing the amount of operation of the oil being analyzed, you should consider the test conclusive only if it indicates a problem. A good report could result from either no problems or a short length of service of the oil.