Engine down speeding is rapidly picking up momentum in the many segment of world market. Numerous engines down speeding packages from OEM have been tailored to take advantage of the increased efficiencies associated with engine down speeding. Running at a lower rpm provides numerous advantages. The most obvious of these is reduced fuel consumption, since the engine can spend more time running within its optimum efficiency range. By down speeding, the engine is made to run at low speeds and with high torques. For the same power the engine is operated at higher specific load (BMEP) which results in higher efficiency and reduced fuel consumption (BSFC). The reasons for increased fuel efficiency are reduced engine friction due to low piston speeds, reduced relative heat transfer and increased thermodynamic efficiency. In the ever increasing demand for further advantage in efficiency and to decrease the emission levels of the internal combustion engines an attempt is made in this experimental work to study down speeding in light commercial engine. The detailed test results along in performance and emissions shows the behavior of down speeding in 3.77 lts of engine tested during the development activities. Keywords: BSFC, BMEP, down speeding etc.