This paper is intended to provide a worldwide overview of the forces driving changes in diesel engine oil specifications. The discussion will start with a review of shifting market profiles as defined by API performance categories and proprietary original equipment manufacturer (OEM) requirements in North America. New performance specifications include API CG-4, CF-2, CF and PC-7. The key elements of these upgrades are changing lubricant quality to meet the design changes necessary to comply with greatly reduced exhaust emissions and modern engine technology. Such design changes bring higher operating temperatures, reduced oil consumption and higher levels of oilborne soot which combine to require higher performance lubricating oils.Following the same format, the current market profile and technical issues surrounding diesel engine technology in Europe will also be reviewed. This will include recent industry (OEM) developments, as well as new Association des Constructeurs Europeenes d' Automobiles (ACEA) diesel specifications such as TD1, TD2, TD3 and TD4. In the forefront will be the impact of on-highway diesel emissions requirements and fuel sulfur level changes on new diesel engine hardware.