In situ testing of fuel oil has become a key task for machine and engine operators. Globally, stricter air pollution requirements require careful monitoring of sulfur content in fuels. Analysis of wear metals and fuel additives helps operators avoid costly downtime caused by engine failures. Energy dispersive x-ray fluorescence (EDXRF) is a common technique used for these tasks. Traditionally, this was done on benchtop EDXRF systems. In recent years, because of performance increases, handheld X-ray fluorescence (HHXRF) analyzers are more commonly used for tasks previously reserved for benchtop systems. We demonstrate that HHXRF can appropriately measure sulfur at low levels, in accordance with ASTM D-4294. We also demonstrate that HHXRF can detect various wear metals and additive elements at low ppm levels—a performance that is comparable to several benchtop systems.