According to Argus there are problems with the processing of Permian West Texas Intermediate (WTI) crude oil. Natural gas liquids, NGL, and additives are being blended upstream into WTI in an effort to boost profits in the face of low prices for crude oil. This is causing processing problems downstream. The problematic NGL component is butane.

The purpose behind adding NGLs is to lighten the WTI into a higher grade. Refineries not accustomed to receiving WTI that has been lightened with NGL are having problems with excessive light fractions that the refinery was not designed for. Crude enhanced with NGLs produce a higher output of light end yields, leading to production bottle necks. Further, the NGL enhanced crude is less dense and occupy more space in pipeline than does typical crude. As of the time of the report by Argus, is was unclear where the NGLs are coming from. NGLs are naturally found in crude oil.

Mercaptans are increasingly problematic, especially for export to countries with more stringent requirements for sulfur. Sulfur compounds are destructive to refinery operations and are subject to regulatory restrictions in some fuels like diesel and jet fuel.

Offshore US Gulf medium sour Mars refers to oil produced by a platform in the Gulf of Mexico and it serves as a benchmark for quality. Recently zinc contamination has been found in Mars crude stream. This has led to supply chain interruptions and refinery problems.