Our presentation addresses the critical challenge of maintaining hydrogen purity in fuel cell electric vehicles (FCEVs) by investigating potential contamination arising from greases used along the hydrogen fuel path. Owing to the sensitivity of PEM fuel cells to impurities—as defined by ISO 14687:2014—the work evaluates both the experimental methodology for assessing contamination and the performance of a specific MOLYKOTE® grease product intended for hydrogen fuel cell applications. Using a state-of-the-art test facility capable of replicating real-world fueling conditions (SAE J2601 protocol, pressures up to 700 bar, and a wide temperature range), hydrogen gas analysis and particle measurements were conducted in compliance with ISO 14687 standards. The results confirm that the adopted methodology reliably quantifies the impact of grease-induced contaminants on hydrogen quality and demonstrates that the evaluated MOLYKOTE® product, MOLYKOTE® HP-300, meets the stringent purity requirements for FCEV fuel systems. These findings not only validate a robust assessment framework but also support the safe integration of MOLYKOTE® HP-300 into hydrogen fuel cell technology.