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Lean burn and EGR are two commonly used technologies for improving fuel consumption and controlling emissions. Each has advantages and disadvantages when applied to an engine and, qualitatively at least, these effects are well known. To meet future emissions and fuel consumption constraints, most production engines are likely to use one or the other. This paper describes testing undertaken to quantify the opportunities that each strategy offers on a production engine. The engine used in this test program was a modern, four valve per cylinder l-4, with high charge activity features including one high swirl port per pair and one straight port with a deactivation plate. This engine is designed to operate with mixtures as lean as 24:1 during normal operation. It was tested at a number of part load operating conditions typical of an emissions drive-cycle over a range of air-fuel ratios.