I am new to the forum have an 01 f-350 7.3 in the last 5 to 6 months I noticed my mileage dropped from around 18 on highway to 12 on highway and in town haven't change a thing. first I changed my fuel filter and nothing. Then I bought a KN air filter kit and still nothing. so I took it to locall dealler. 80 some dollars later they hook up senser and no codes and tell me nothing is wrong. checked my brakes thinking maybe they are stuck. Then i take it to the GM dealer found a vacum hose not connected but did nothing. any help

 

Could be one of your 02 sensors are going bad, but not showing an error yet.

 

seeing as my old saturn had major EGR problems... that's always the first thing that I think of to check.
Do you have any other symptoms other than the drop in mileage?

 

`FIRST OF ALL YOU DONT HAVE O2 SENSORS OR EGR ON THIS TRUCK WATCH WHERE YOU ARE GETTING YOUR FUEL BE SURE THATITS OVER 40 CETANE AND DONT GET IT FROM ANY BULK STATIONS DUE TO THE EPA RELEASED FUEL WITH LESS ADDITIVE IN DUE TO KATRINA FOR THE BIG TRUCKS DUE TO HIGH COST LET ME KNOW IF THERE ARE ANY HARD STARTING IN AM AND HOW MAY MILES ON TRUCK AND WHAT WEIGHT YOUR PULLING HOPR THIS HELPS SOME