An engine in a characteristic vehicle sized to produce the desired power for speeding up, but also has to operate well points in the normal stable speed operation. The additional work done by pumping the air from beginning to end the throttle, which reduces competence. If the ratio of fuel or air reduces, then the power will achieve with the throttle close to completely open. The efficiency of the driving can be elevated. When the engine runs with the help of more air and less fuel, it called as lean burn. It has a very weak mixture of ratio 18:1 air or fuel instead of making the ratio 14:1. It reduces the level of exhaust pollutants like carbon monoxide and unburnt hydrocarbons. Hence, no engine can run on this lean. The engine needed to have cautiously controlled ignition advance. It is a specially designed for combustion chamber that has a very strong effect. Direct injection engines can achieve by this ratio.