Provided are a borosuccinimide compound obtained through reaction of (a) a succinic acid/anhydride substituted with an alkyl or alkenyl group having a number-average molecular weight of from 200 to 5,000, (b) a polyalkylene-polyamine of which at least 5 mol% has a terminal cyclic structure, and (c) a boron compound; and a succinimide compound obtained through reaction of (A) a succinic acid/anhydride substituted with an alkyl or alkenyl group having a molecular weight of from 200 to 5,000, with (D) a hydrocarbon-substituted polyalkylene-polyamine. These compounds are stable even at high temperatures and have good high-temperature detergency, and they are useful for ashless detergent dispersants having the ability to disperse fine particles. Also provided are a mixture of any of these compounds and a specific ester derivative; a lubricant additive and a fuel oil additive comprising the mixture as the essential ingredient; and a lubricant and a fuel oil composition containing the additive.