I have a 1999 Doge Durango SLT V8 5.2

I am averaging about 9mpg. A co worker has the EXACT same model and averages 14/15. A changed out my plugs cuz they were pretty nasty and I still roughly get the same thing. What could be causing such bad mileage?

Thanks!

 

First of all, no two cars will EVER be the same.

Second, you may want to check your plenum gasket. You can do this by looking down your throttle body, and looking for large deposits of oil.

Third, you could check your catalytic converter. Bang on it with a rubber mallet, if it rattles its toast.

Fourth, you can check your O2 sensors. Could be fouled up, and producing a lean condition in which the computer corrects by dumping in more fuel.

Fifth, I'm sure there are other things that can be done, but I feel this is a good starting point.

 

to add to Joe's list......

sixth, You bought a 5000k brick, don't expect to have too high of numbers where MPG's are concerned. My 5.2l averages about 12 in the city and 14 on the highway.

Also, how are you getting your #'s? don't trust the overhead calculations... mine says i average 7mpg!

 

Change your air filter, and get new pre-cat O2 sensors. I get them from www.rockauto.com and I get the DESNO brand and make sure I get the OE style so they are plug and play.

 

Mine doesn't have the overhead screen that says the mpg. I do it by filling the tank and divide the miles by gallons.

 

I'm not trying to rob the thred, but are all the o2 sensors the same? As far as upstream, downstream, and ca emissions? Or are they all different part numbers?

 

AFAIK, There is a upstream part # and a diff downstream part # .. i would assume on a cali setup its the same part #'s just you need 2 of each rather than one on a federal setup.

 

Try runnin some Seafoam through the intake and gas tank. That will clean the valves and injectors. May help.

 

Well it was made in the late 90s at a time when gas was around $1 gallon so these late durango had very bad gas mileage cause of that. My 2002 ram 1500 4.7 is very thirsty as hell! Average is 12 mpg, normally 11mpg and on few times 9-10 mpg! Just bought KN filter and now it doing 13 mpg. 2005 and below the engines were not fuel efficient only from 2006 and later. Thats has to be the reason.

 

your RAM gets horrible gas mileage because it is a big heavy truck powered by a small v8, the durango is a smaller truck, and in ALL model years is capable of better mpgs than that, i reuglarly get 17 around town an 19 on the highway in my 2002 with the 4.7 in it.

the other major factor is how heavy your right foot is