Taking utmost consideration in delivering the best possible fuel economy, your engine is equipped with Audi A4 Oxygen Sensor to determine how well fuel is burnt though your engine combustion operations. Engine runs at its best when the air-fuel mixture is correct. By effectively measuring the oxygen proportion of your fuel exhausts, your system could measure up its combustion performance which enables the system to make all the necessary adjustments needed to sustain smooth operations achieving lowest emission levels. A thick air-fuel mixture indicates poor combustion efficiency and too lean mixture may indicate that damages are already brewing among your combustion or exhaust system components. Enabling your engine systems to make all the necessary adjustments to boost fuel efficiency and overall engine output, it must be kept in top notch working conditions to continually rake performance and fuel efficiency gains. With routine check and periodic replacement, you may eliminate the risks of failure with significantly minimized fuel wastage. Good thing Replacement USOS-4000 is conveniently available as practical solutions to maintenance. Fitted for your 1997 - 2006 Audi A4 Oxygen Sensor application, it is designed to makes use of factory fitment settings for hassle-free installation. Poor drivability may be manifested by an already faulty or damaged oxygen sensor causing premature damages to the catalytic converter. Once your stock sensor starts fouling up, you may experience decreased fuel economy, hesitation on acceleration, stalling, surging, rough idle, and increased tailpipe emission which most likely fails emission tests. For your next Audi oxygen sensor replacement, take advantage of the fuel efficiency boost offered by heavy duty Replacement Oxygen sensors. Seal premium deals with us right at your fingertips.