Hi guys im new to the dodge scene just bought my first dodge 2004 5.7l 4x4 It has 120k on it. I'm getting 8.8mpg I manually calculated it. The best Ive got was 10.4mpg when I was driving like a granny. I have KnN intake, Cat Back Magna flows, I checked a few plugs none of them are fouled. Any advice would be appreciated

 

When was the last time the plugs were CHANGED? Also, any lift? Stock-sized tires, or are you running on wider 33's or 35's or larger?

 

No clue on the plugs. No lift and 285/70/R17's

 

Look to the obvious first - TUNE UP... Biggest MPG robbers after that would be a dirty throttle body (should be cleaned every 30k miles max), dirty EGR valve and under-inflated tires...

 

What is the gap on those plugs? Are you compensating for the speedometer/odometer error? Clean the TB, clean/replace the PCV valve.

 

I'm kinda in this same boat. My 07 4x4 has 55k miles on it and I've been gettin 7.5 (so my computer says). I did get bigger tires and haven't gotten it recalibrated yet however I did the math and I'm 99% sure that the recalibration will only add about .5 MPG. I just got the truck 5 months ago and am not sure what the previous (original) owner had done on it. I just changed my plugs myself from the stock champion coppers and put in champion double platinums. It does seem to run a little smoother but still not sure about the MPG because I only changed them last week but so far its at 12 and still dropping slowly after a long highway drive.

Maybe a tune up would do the trick?

No lift but I do have 285/70/R17's

 

I'd say something would be in order.

I get about 13 mpg in over-all use and hit about 16.5 on trips that are mostly interstate and highway driving and my truck weighs in at about 7000 lbs. with me in it, my toolbox jammed with heavy sh*t, a full sub-frame on my suspension lift, winch, etc. I do have a few mods that may be giving a little mpg side benefit along with the power gains...

 

Even I average 9.9 - 10 mpg in town. My biggest problem is probably my right foot, although on the highway I never top 14 mpg. I don't worry about it anymore because the truck does do everything I want it to.

 

I would go back to the coppers the next time you do a plug change. The extra money you pay doesn't make any difference in fuel economy or performance. The hemi engines are engineered to run the best on the champion coppers. Just my two bits!

 

I had a 2005 hemi, best i ever saw was 10 to 12 mpg highway at best.
Tune it up, pump the tires up 40psi, synthetic motor oil, and hope for the best.