Abstract: Premium coke having a low coefficient of thermal expansion and containing reduced fluff coke is obtained by subjecting an aromatic mineral oil to reduced temperature delayed coking, thereafter converting uncoked oil in the coke drum to coke under delayed coking conditions by continuing coking in the presence of a aromatic mineral oil capable forming coke admixed with a non-coking material circulated through the coke drum as a heating fluid. After termination of the heating fluid, the coke in the coke drum is subjected to a heat soak in the presence of a non-coking material at an elevated temperature preferably above the delayed coking conditions.