Could be tires/wheel alignment, suspension, transmission and brake problem causing it to reduce mileage, also running rich due to the following below
1. Excessive fuel pressure can be cause by restricted fuel return line
2. Defective Oxygen Sensors.
3. Leaking injectors and fuel pressure regulator.
4. Coolant temperature sensor out of calibration.
5. Restricted air intake system.
Monday, May 7th, 2012 AT 7:30 AM