Visbreaker residue is only slightly more pleasant. To produce fuel oil, lighter products need to be blended in. Light cycle oil has the consistency of diesel fuel and paraffin. Heavy cycle oil has a consistency similar to golden syrup. When combined, these various refinery materials make fuel oil.
Bunker fuel is made from a succession of process residues.
It is worth noting that refinery managers are guided by economic principles. If the price of bunkers compares favourably with that of higher end products, they will set the operation of their plants to produce more heavy fuel oils. Given the opposite circumstances, managers will squeeze more light-ends out of their crude. It is a case of maintaining optimum ratios to produce an optimum return on the crude input. It should be clear that bunker fuels are not a waste product.