It is possible to have a clean green diesel engine with low exhaust emissions and excellent fuel economy. The two major requirements for this engine are a low sulfur diesel fuel to permit the application of emission controls, and the support of effective regulations and standards.The diesel engine is a major contributor to air pollution - especially within cities and along urban traffic routes. Because diesel engines are extremely durable - lasting for 20 to 40 years, once they are introduced in an area they contribute to the air pollution problems for decades. Off-road vehicles further contribute to the pollution problem. Consequently, India needs to devise an emission control strategy that addresses both new and old engines. In addition to the normal components of air pollution that cause ground level ozone and smog in the atmosphere, diesel exhaust also contains particulate and hydrocarbon toxic air contaminants (TAC). These pollutants pose additional human health concerns. Diesel particulate matter (PM) is made up of very small particles that are inhaled deep into the human lung. Since there is no effective natural removal process from this area of the lung, the particles remain there. These particles are an increasingly urgent health concern.The first step toward a solution is to set up a framework for new engine emissions regulations. The second step is establishing a program for the older high polluting engine currently in-use. In order for these initiatives to be successful, India must revise the diesel fuel specification to a low sulfur fuel -at least below 0.05% sulfur content. With these provisions in place, cleaner new diesel engines will replace older engines. Furthermore, the older in-use engines, which would be in service for another 20+ years, can be made significantly cleaner with ‘retrofit’ and ‘engine rebuild’ programs.Today's engines can be retrofitted to run cleaner. As worn-out engines are periodically completely taken apart and rebuilt, they can be upgraded to include the latest emission controls technology.The effects of diesel fuel sulfur on the engine and emissions control technology is discussed in this paper. Ultimately, low sulfur diesel fuel is the first step required for India to achieve their clean air objectives. Once the fuel is improved, emission control technologies can be fitted. The current available emission control technology options and achievable emission control limits of each are outlined. A program for action is suggested.The support of diesel engine manufacturers is needed in order to most effectively apply emission control technology to new and old engines.