Beginning January 1, 2007 on-highway diesel engines faced tougher emission standards for NOX and particulate matter. Over the course of the subsequent three years, NOX emissions will have trended down toward the 2010 standard, mentioned above. This phase-in provision allows the engine manufacturers to concentrate on reducing NOX. On-highway fuel sulphur levels have dropped to 15 ppm, beginning in 2006 because even relatively small amounts of sulphur add to particulate exhaust emissions. To achieve these emissions limits, OEMs are using a combination of cooled exhaust gas recirculation (EGR) at higher rates and exhaust after-treatment devices such as catalytic diesel particulate filters and oxidation catalysts. This has resulted in a new generation of engine oils that provide emission control system durability, prevent catalyst poisoning and particulate filter blocking, while still offering optimum protection for control of piston deposits, oxidative thickening, oil consumption, high-temperature stability, soot handling properties, foaming and viscosity consistency during shearing. These increased demands on the lubricant fluids require more accurate and reliable condition based monitoring. There are two distinct drivers in the mobile asset on-highway (trucking and commercial automotive); 1) extending oil change intervals in commercial vehicles, and 2) optimizing and extending warranty on diesel engines in truck engines. In this document the focus is on the diesel engine market due to the urgency demonstrated by the market. Finally, it is important to note that for truck engine manufacturers, the requirements of any System for the determination of diesel oil quality is driven by their desire to rapidly and continuously monitor fuel dilution and soot loading (and possibly contaminants depending on usage conditions) in addition to traditional trend analysis of additives content (TBN, etc.).To this end there is an unmet need for an in-line process monitoring device meeting the needs of the market. The present work shows progress towards a system that overcomes many of the limitations of prior sensor systems.