I got a 08 Dakota 4.7L V8 SLT crew cab with 62,000 miles. Over the past two week my gas millages has gone down severely. The only thing that was done to it was a ECU reset. Before the reset I was getting about 11.2 MGP. I am currently getting 9.4 MPG and it is still falling. No change in my driving style or anything. I am always keeping an eye on my MPG but it has never been this bad or gone this low. Does Anyone have any idea what might be causing the bad millage. Was it the ECU reset that screwed it up or is that just a coincidence?

 

After an ECU reset, the fuel trims may take some time to re-learn.

I know you said there was no change in your driving style, but what about a change in your average trip distances from cold start? Any shorter trips, on average, than before? Did your job recently move closer to home, for instance?

 

There had been no change to the distance I drive. I only have a 6 mile drive round trip. Almost not even enough time to get the truck warmed up. Since it has gotten cold out I have been starting the truck up and letting it warm up for a few mins before I take off and drive it. I have always done this in the winter but it never made the MPG be this low. Maybe I need to do another ECU reset and drive it for a long distance to reset the fuel trim. See if that has any effect.

 

Some areas do the winter blend gas also.

 

you need to start doing hand/mpg calculations. fill truck and zero trip odometer, go for a long drive, 300 plus miles on interstate, calculate, then fill up again and reset odometer and come home and calculate. never go by the overhead console. I get pretty close to 400 miles out of a tank. but when I fill up the gas is just to the top of filler neck, my truck says 320 mile to empty, but my console doesn't start to deduct the DTE until around 80 miles or so of driving. but starts adding the miles when reset to zero. Somewhere I have a video on this site showing everything

 

another thing, check your tire pressure, I normally run 40 psi

 

11.2 MPG before it went down?

11.2 MPG sounds very low to me. Living near Buffalo NY, I also have a 2008 4.7. I became concerned when mine went down to 12.9, but that was during a recent cold, snowy spell and I was using the remote start on my Dak a lot - even warming it up close to a 1/2 hour.

I only drive about 8,000 miles a year and it's about a 75% city 50% highway mix. I use the auto start and let it idle during cold spells in the winter and hot spells during the summer to get the climate control going. I average in the low 13's during the winter and mid-15's in the summer. And I do somewhat have a heavy foot at times.

And I'm overdue at 55,000+ miles for a spark plug change (original as far as I know - bought it used at 18,000 miles).

You may have something going on for the low MPG.

I should add that most of the time I'm running non-ethanol gas which in the past gained me an extra 1 MPG which almost off sets the increase in cost for the non-ethanol.

PS - I have on occasion traveled to my sister's home in Rochester, NY which is 1 1/2 hours away door to door (1 hour highway doing 70 MPH), and have reached 21.5 MPGs on the round trip. I'm sure I could have reached at least 23 MPH doing 55 MPH which from my understanding is the optimal speed for best MPG.

 

Wow thats awesome gas millage. I can definitely say I have never gotten that. I have tried a lot of different thing to get mine back up but nothing has helped. I did a tune up, spark plug change, I did fuel injector cleaner, checked tire pressure. I even did the math myself to see if my computer was screwed up but it's not. In fact my computer says I'm getting .3 more per mile than my math came out to. I hooked my Autel Scanner to it. No codes, live data seemed ok from what I was able to understand of it. I'm starting to think that I have some type of transmission problem, that's the only thing that would explain that much gas consumption, not shifting properly. All I know for a fact is that I am at a total loss. I just hope I can figure something out soon cause I'm at a point where if I am gonna keep get bad gas mileage I am better off trading it in for a bigger truck that gets better millage.