Environmental issues and energy security are critical concerns of the most countries. According researchers, excessive growth of land vehicles is one of the biggest contributors to global air pollution and oil reserves reduction. In this context, the use of lean burn technologies emerges as a promising strategy, allowing lower fuel consumption and pollutants emissions. Present work aims to analyze the behavior of a current commercial engine, gasoline fueled, varying the air-fuel ratio without the use of lean burn ignitions technologies. Analysis was performed through bench dynamometer tests, evaluating cylinder pressure, exhaust gas temperature, fuel conversion efficiency, cycle thermal efficiency, coefficient of variation in indicated mean effective pressure, apparent heat release rate, flame development angle and burn duration. As expected, mixture impoverishment caused a progressive increase of burn duration, flame development angle and coefficient of variation in indicated mean effective pressure and a decrease in exhaust gases temperature. Difficult operation of the catalyst due to the exhaust temperature reduction and the significant increase of combustion variability, pointed out by the experimental results, reinforce the importance of the use of techniques for adequate lean mixtures burning.