the precipitation of sediment in the unconverted residuum derived from a virgin residuum conversion process is reduced significantly by blending with the uncoverted residuum an effective amount of a virgin residuum having an asphaltene content of at least about 8 % by weight of the virgin residuum at a temperature sufficient to render both residua during blending at a viscosity of no greater than 100 centistokes . a blend of 1 - 20 % virgin residuum containing at least 8 % asphaltene with 80 - 99 % unconverted residuum from a virgin residuum conversion operation , which will contain little , if any sediment , can be used as heavy fuel for power plants .