An analysis was performed to determine the effects of fouling of the preheat train on the energy efficiency of a typical crude-distillation unit with a capacity of 100, 000 bbl/day. A spreadsheet analysis was developed to calculate the thermal duty for each of the hear exchanger groups that heat the crude oil from ambient conditions to the distillation temperature. A fouling-rate model del eloped in a previous study was applied to calculate the fouling resistance as a function of time. Improvements in the energy efficiency were analyzed for different mitigation scenarios. The analysis shows economic incentives for new and improved techniques for mitigating fouling of the preheat train.