Poor fuel mileage

I have an 03 F-150 supercrew 4.6L V8. The mileage has gone down noticeably in the last month, no change in my driving habits. Cleaned the MAF sensor. No codes come up on the computer. What is the likely cause?:cool:

Check the operating temperature a thermostat stuck open will cause this condition. Ask the parts store who scanned the engine what temperature the scanner read. Some times the computer temperature sensor will get scaled up and you can clean it with steel wool.