201522 - Call 01

New York
Marc’s gas mileage began dropping, so he got the car tuned up. Then the mileage drop got worse, his mechanic said the tuned oxygen sensor noticed a crack in the exhaust manifold, so Marc replaced the manifold, but the mileage has continued to drop. It’s gone from around 30 MPG to under 20 MPG. The problem is likely a bad thermostat, though there is a slight chance the transmission is slipping.