Abstract: Hot surfaces of heat exchangers in oil refineries are easily exposed to fouling and it has been a major problem to overcome, particularly in crude preheat train. The crude oils together with their blends have been known to cause significant fouling due to its composition, incompatibility and effect of operating conditions. This study focuses on the composition of fouling deposits with regards to crude oil properties. The study on the asphaltene as fouling contributor was conducted where asphaltene precipitation factors analyzed using Design of Experiment analysis, Taguchi Approach. Besides that, crude oil incompatibility analysis due to asphaltene drop-out using an Automated Flocculation Titrimeter was also conducted. The analyses were conducted for two Malaysian crude oils. Data on crude oil characteristics, asphaltene precipitation and flocculation are presented and the fouling behaviors in Malaysian crude oils are discussed.