Thai Oil refinery has been designed to create maximum value from the production system. As a complex refinery, the refining process involves various steps that take place in the crude distillation units, the upgrading units, and the quality improvement units, that make Thai Oil becomes one of Asia-Pacific's leading producers of high quality petroleum products. It also allows for flexibility in using raw materials or crude oil from various sources, and in adjusting the production level of each type of petroleum product to be in line with domestic demand.