Introduction The imposition of maximum sulfur specifications on fuel oil through clean air legislation results in higher costs1 for fuel oil suppliers. Thus@ there is a clear-cut@ economic incentive to the petroleum industry to minimize unnecessary giveaway on fuel oil sulfur content so that low sulfur fuel oil can be supplied at minimum cost to the consumer. There is also an obligation on the part of enforcement officials to administer the laws so that they do not impose more of a burden on suppliers and consumers than was intended. Prime factors in minimizing giveaway while assuring compliance with the law are the precision and accuracy of the test method used for determining sulfur content. Clearly@ the ideal situation would be one where the petroleum industry@ governmental agencies and major consumers could each determine true sulfur content with absolute certainty. If this were so@ fuel oil could be supplied with sulfur content close to the specified maximum and have no worry at all that governmental agencies would conclude that the sulfur was over the legal limit due to test variability. 1. Desulfurization Costs - Residual Fuel Oil@ Bechtel Corporation for the API@ February@ 1967. Based on figures from this report@ each additional 0.1% sulfur giveaway would cost Caribbean industry about $20 million per year to supply U.S. East Coast demand.