AbstractRecent design trends of automotive petrol engines, brought about by the need to meet exhaust‐emissions legislation, are discussed. It is explained why many of the consequent changes have the side effect of seriously increasing fuel consumption. the conventional inlet system is isolated as a major cause of poor combustion, which leads to the presence of much of the pollutants, and to low engine efficiency.A historical survey is included on the events leading to the present‐day exhaust‐emissions legislation, and the sources of, effects of and conventional methods of control of the major pollutants are discussed.An alternative approach to the reduction of exhaust emissions has recently attracted interest. Mixture preparation as a means of delivering a near‐homogeneous mixture to the engine cylinders has the combined effect of reducing exhaust emissions and fuel consumption. A survey of research and recent applications of this method is included.A method of achieving a near‐homogeneous mixture which is simple and effective, and which has been developed by the authors, is described. the results of a lengthy programme of tests in both a laboratory situation and in a car ‘on the road’ are presented and discussed. the encouraging conclusion is drawn that this approach (mixture pretreatment and lean mixture) does indeed result in cleaner exhaust gases and reduced petro