In this study, we examine the link between stability of asphaltenes at ambient conditions with fouling at the conditions of a delayed coker furnace, with heat-transfer surfaces above 450 degrees C. The atmospheric bottom fraction of a crude oil was blended with an aliphatic diluent in different ratios; the S values were measured; and then fouling rates were measured on electrically heated stainless-steel 316 wires in an autoclave reactor. As expected, the less stable the blend, the greater the rate and extent of fouling. The most severe fouling occurred with the unstable asphaltenes. Scanning electron microscopy (SEM) imaging of the foulant illustrates very different textures, with the structure becoming more porous with lower stability. Under cross-polarized light, the coke shows the presence of mesophase in the foulant layer. These data suggest a correlation between the fouling rate at high-temperature furnace conditions and the stability index of the crude oil.