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legendarith said:
Is it true that a broken Oxygen (O2) Sensor affects your gas mileage by decreasing it?
In some cases.

Typically, as O2 sensors "wear out", they give a false rich signal to the ECU. The ECU then tries to lean the mixture. Net-net, fuel mileage is better with a worn sensor.

When I replaced both front and rear sensors a few months ago, my mileage dropped 1.5 MPG.
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