I had a post back in February....I have an 05 Dakota Quad Cab, V8 4.7. My gas mileage has been horrible since late fall. The truck seems to idle a little rough too. There have been no check engine lights. The dealer replaced the O2 sensors, but no change. I just traveled 80 miles, 40 hwy and 40 stop and go city, I got 8MPG. I tried the auto lite plugs, a K&N drop in filter and injector and fuel system cleaner. Any other ideas as to what could be wrong?

 

Wow, uhm.. holy crap...

My dad gets better mileage in his Hemi, under full load, lol, he averages about 13 mpg while plowing...





Did you bring it back to the dealer, and tell them you are still getting crap for mileage?

Wow, I have NO idea what this could be... I get roughly 18 - 20mpg on highway, and about 16 in town, in a 4x4 6spd v8...

 

What kind of gas are you using. When I got to Hawaii all the gas here has E10 in it. My mpg dropped to about 10-12. So you might want to check if the gas station you are filling up at is using E10 or not. Just something to look for.

 

I've had it back to the dealer, they said that they re-calibrated the computer. That was last week.

 

two things could be causing this a bad egr valve that is stuck open or a bad cat converter. plus check your tire pressure. i run mine at 40 psi on all 4 tires. better then the factory setting at 35 psi. also winter blend gas just sucks

 

umm i really dont know what to say to help, but that definetly isnt right, i get 13-14 in the winter,

and i think im starting to get summer blend gas my mpgs are almost at 15(my low in the summer)

 

Would a bad EGR valve cause a check engine light?