A survey was conducted at a number of heat-plant installations at bases in the Eleventh Naval District to determine the need for the use of additives to prevent sludge in No. 6 fuel-oil storage tanks. The fact that no sludging problems could be found at bases not using an additive indicated that a need did not exist. Several of the facilities reported that additives decreased the formation of soot by improving the combustion. A test was made to check the validity of these claims. An additional test without additive showed that changes in operating schedules would also reduce soot accumulation. It was concluded that no requirement exists for additives for sludge prevention. It was further concluded that combustion catalysts are beneficial for boilers operating under intermittent and cycling conditions, but that no substantial benefit results from the use of catalysts when boilers are operated continuously.