I'm about ready to just sale this thing and be done. I spent 4 hours changing the up stream 02 sensor cause dodges dumb design. and no luck! a full tank i got about 147 miles! its a 4.7l 4x4 and the tires are bigger then stock but theres no way thats causing this much drop. it never got good mileage or what other durangos get but 6-7 mpg is crazy. it has a new air filter and oil change. pulled the plugs and all look the same and have about 3000 miles on them. changed the upstream o2 it only has 2 02 sensors both before the cat on the left side.. strange.. so if both are before the cat do both need tobe replaces and why is there not one after ? also has a new pcv valve. and air filter I dont smell gas leaking. cleaned throttle body. i'm just at a lost I hope someone can give me some answers cause im done.

 

how are you calculating your mpg? if you are using the numbers from your tripmeter they are wrong, the truck is going farther than that with taller tires.

if i were you i would get a gps to figure out the calibration factor, and then use that to figure out true mileage and calculate MPG using that number

 

What size tires? Also did you buy it and it was this bad or did all of a sudden it just got worse. Please elaborate, also you should have an O2 sensor after the cat, if you don't that could be the issue.

 

the after cat o2 sensor does nothing but monitor the cat efficiency, it has exactly 0 effect on gas mileage or engine performance

 

there 265-75-16 and i've used the trip and the cluster that tells you how many miles till empty. i'll try to use the gps and i'll double check for a 02 after the cat again but when i was down there i only saw 2 before the cat and it all looked stocked until i had the muffler taken off and had a flow master put on. and it seem like at best maybe 12mpg and in the last 2 months is when i notice worse mileage and you just kept getting worse the idle seems low but normal and steady i'll check what rpm it sits out

 

Update. replaced upstream o2. has help mpg but don't know how much yet im still trying to figure out how many mpg im getting. if anyone has a easy way lmk. my gps was 10.8 and my trip meter was 11.3 miles. so not off real bad.it does has a 02 after the cat it was hidden on top. what is everyones city mpg with the 4.7l durango?

 

Fill your truck up. Drive around then fill it back up again. Divide the miles and how many gallons it took to fill up. Example: 300 miles divided by 10 gallons would be 30 MPG.

 

That would only work if his tires were the stock size and/or the speedometer was calibrated to match his tires upgraded size. Regardless anyways I am also running 265/75/16 tires with a 5.9 motor, but my overhead reads about 11-12 mpgs. I know it's off due to tire size, but it's not reading 6-7.
I don't know much about the 4.7's but I haven't seen anyone mentioning resetting the computer.

 

DON'T RELY ON THE OVERHEAD COMPUTER PERIOD! The only thing i use mind for is the direction and the temp and even then sometimes it not right... My overhead always tells me me that i am getting 7.9MPG :FAIL:

Also, when i first installed my overhead console i was watching the DTE.. driving down the highways the truck sputtered and dyed.. WITH 6 MILES TILL EMPTY on the overhead. I always carry a 1gal can of fuel for incase *hit happends... put it in and the truck started up.

Since you changed the front O2 sensor i would look for exhaust leaks if in fact you do determine you truly are getting 6 MPG. I know when i changed mine i found that the stud that the rear sensor was on had rusted and the sensor was just sitting in the pipe.

 

Sorry for the last reply I forgot my pw and this site seems to take days to send you a reset. but seem like mpg has gone back down. im maybe getting 10 mpg at best with granny driving. just don't get how it can run. not have codes yet be off this bad .ran fuel cleaner. tune up should still be good. cats good replaces upstream 02. just dont know what else to do. everyone gets 12-17mpg city normal driving and im not getting close. could it be sludge thats causing this ? at idle my oil pressure is right above the 1-4th mark and driving normal its about 2-3rds. ive ran rislone engine treatment in the last 2 oil changes idk im lost