Your Buick oxygen sensors are necessary for your car to get the maximum power, best fuel economy and most efficient emissions. When one begins to fail, you will notice that your mileage is dropping. Your Skylark might fail upon starting, or you will feel the engine hesitating or surging when you touch the gas pedal. The oxygen sensor's job is to tell the Engine Control Unit (ECU) how lean or rich the air/fuel mixture is, and then to adjust the ignition/combustion system accordingly. If the sensor finds a rich mixture, the voltage in the oxygen sensor rises. For a leaner mixture, the voltage drops. The mixture of fuel-to-oxygen is vital for proper combustion. Too many air bubbles in the fuel will cut down on the density of the flow, which changes the consistency of the fuel as it is sprayed by the injectors. If the mixture is too 'lean,' the air-to-fuel mixture cannot sustain combustion, and the engine will misfire. During a lean misfire, the unburned fuel is passed into the exhaust system, which will boost your emissions - and cut down on your gas mileage. When a lean misfire happens, unburned oxygen enters the exhaust and the oxygen sensor will indicate a problem. If the mixture is too rich, your Buick will idle roughly, the spark plugs will be damaged and your car will be slow and sluggish. Order a new set of Buick oxygen sensors and be confident that they will accurately monitor how rich or lean your fuel mixture is running.