Tramp oils (lubricating, cutting and hydraulic oils and greases) have serious, adverse effects on water miscible cutting and grinding fluids. Tramp oils cause a loss of wetting and thereby will degrade both the workpiece surface finish and tool life. They also reduce the cooling effect of the fluid that also impacts tool life. Tramp oils will impede filtration and contribute to unfavorable residues on machine tools and workpieces. Environmentally, tramp oils contribute to smoke and oil mist and stimulate the growth of bacteria.

These adverse effects are proportional to the amount of tramp oil present and, therefore, are most pronounced on those machines which leak the most oil. As bad as these effects are on "individual sump" machines, they are even worse in central systems where continuous recirculation through powerful pumps keeps the oil emulsified.

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