does a bad exhaust manifold gasket cause poor gas mileage?
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2004 Ford Mustang Question: exhaust manifold gasket.
Answer #1dandd December 27, 2009, 22:56Master
Yes, because the fresh air hits the Oxygen Sensors and makes the car run REALLY RICH, which cuts about 40% off your mileage. You may also have a Check Engine Light on as well. This article explains about the Check Engine Light