Crude oil is usually transported by pipelines from the production areas to refineries. However, in North America, particularly Canada, a significant amount of crude oil is transported via specially designed railcars. The internals of the railcars are typically coated with a high-quality coating system to prevent corrosion. Still, coating failures do occur due to the unique cyclic operating service conditions of the railcars. Thus, elevated temperatures are used to reduce fluid viscosity with a resultant increase in the vapor pressure while the loading of the oil in the railcars. Once loaded, the crude is transported under ambient temperature and pressure until the railcars reach their destination. During off-loading, elevated temperatures are again used for reducing the viscosity of the oil. After emptying the contents, the railcars are allowed to return to ambient conditions and sent back to the production area to repeat the loading, transportation, unloading cycle. Currently, there is no established test protocol to evaluate candidate coating systems for railcar internals under simulated operating conditions. Testing is usually done under a single set of operating conditions of loading or unloading and does not include the synergistic effect of the different temperature variations. This paper presents a detailed test protocol for evaluating candidate coating systems for railcar internals. The proposed test protocol was designed to simulate the expected service conditions of railcars using a modified NACE TM0185-2006 test procedure, “Evaluation of Internal Plastic Coatings for Corrosion Control of Tubular Goods by Autoclave Testing”. The modification includes the cyclic service condition of railcars – fuel loading, loaded transportation, off-loading, dry heat and empty transportation.