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Q: dealer replaced oxygen sensor now my mpg has dropped by 5 mpg why

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check engine light came on so dealer replaced oxygen sensor now my miles per gallon has dropped by 5 mpg

My car has 10000 miles.
My car has an automatic transmission.

A: After a part is replaced the computer has t...

After a part is replaced the computer has to be reset to factory settings. In this period of time you may get a fuel mileage change for a few weeks, until the computer relearns drive strategy again. If mileage does not improve in a few weeks then take it back to the dealer to have it checked out. If the Check Engine Light comes back on take it back as well.

If you'd like a second opinion on this, consider YourMechanic, as a certified professional will be able to help you diagnose your decreasing gas mileage and suggest a fix from there. Good luck.

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