Lean-burn gasoline combustion systems have been commercialized by major light-duty vehicle manufacturers in both Japan and Europe, regions where gasoline sulfur levels are capped by regulation at 10 ppm. In the U.S., gasoline sulfur standards are 30 ppm average and 80 ppm maximum. One of the main reasons for adopting 10 ppm in Japan and Europe was to facilitate expanded introduction of lean-burn gasoline engines. Similar arguments have been made for lowering U.S. gasoline sulfur standards.The Martec Group, Inc. has completed an in-depth study on the current and future utilization of lean combustion systems on gasoline engines by global light-duty automobile manufacturers. The study is based on a review of published technical information enhanced through discussions with technical experts across the community of global vehicle manufacturers and suppliers of fuel systems, valvetrain, turbocharging, exhaust aftertreatment and other vehicle subsystems. It defines the cost/benefit of lean combustion and emission control systems compared to other fuel economy and CO2 emissions-reducing technologies that are in commercial development in the global market. These technologies are compared on a uniform basis: variable cost dollar per gCO2 reduced. The rate of commercial adoption of lean gasoline systems in Japan and Europe - regions with existing 10 ppm max sulfur regulations - is defined historically and forecast through 2020. Lean gasoline combustion system adoption is forecast for the U.S. through 2020 based on existing and emerging fleet average CO2 emissions regulations, tailpipe criteria emissions regulations and under scenarios whereby gasoline sulfur levels are regulated to 10 ppm max and to 10 ppm annual average limits, respectively.The study concludes that the market penetration of lean gasoline direct injection (GDI) engines in Europe will peak at about two percent (2%) in 2010, the same maximum penetration level the technology reached in Japan 10 years ago. As in Japan, lean GDI will not be a meaningful technology path for European fleet average CO2 compliance beyond 2013. In North America, the opportunity for lean GDI will be limited to a narrow number of naturally-aspirated engines that cannot accommodate advanced variable valve timing, a building-block technology necessary for HCCI functionality. Between 2015 and 2020, the maximum potential share for lean-burn engines in the U.S. is projected to reach three percent (3%), and decline thereafter as observed in Japan and Europe.