Lean Mixture combustion engines are attractive because of the low emissions and good fuel economy that are possible with a properly designed lean burn engine. Toyota Motor Company Ltd. has developed several small displacement (under 2 litres) lean burn engines, and early this year began selling a lean burn vehicle in Japan. The Emission Control Technology Division (ECTD) has recently tested several prototype lean burn vehicles. When Toyota offered to provide EPA a lean burn vehicle for emissions testing, ECTD was pleased to have the opportunity to evaluate this new technological development. The conclusions from this EPA evaluation test can be considered to be quantitatively valid only for the specific test car used. However, it is reasonable to extrapolate the results from the EPA test to other types of vehicles in a directional or qualitative manner, i.e. to suggest that similar results are likely to be achieved on other types of vehicles.