<div class="htmlview paragraph">A summary of theoretical considerations that motivate the development of lean burn systems is presented along with a review of the most common approaches used to implement this technique. An analysis of experimental data from several sources is then introduced in order to substantiate the advantages and indicate drawbacks encountered when implementing lean burn vehicles. It is concluded that at the present state of development, U.S. emission standards present a considerable challenge to the realization of the fuel economy advantages theoretically inherent to lean burn engines.</div>