I highjacked another guys post with this, and didn't get any responses. So I'll try it again here[8D]
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My 2003 4.7 4x4 Quad Cab only gets 11-13 mpg.

I have 265 75R 16 All Terainson8" wheels.
K&N CAI
Magnaflow 18" Exhaust.
But other than that everthing else is stock.

It was recently tuned up at 36,000 miles,I only put Mobil Synthetic Oil in it, and I always run REGULAR unleaded gas. I just put the CAI & Magnaflow on it a week ago. I went through my first tank of gas, and found thatit didn't do any better in the mpg catagory (12 mpg). Half of that was Highway, and the other half was city (about average for me).

Should I take it to a Dodge service shop, and have them check it out? What could possibly be causing it tobe this bad??? HELP[&o]
FYI: When I first got it (new) in 2003, it was averaging around14-16 mpg with stock wheels & tires.A month after I got itI put on 275 75R 16 Radial Mud TA's, andit went down to 10-12 mpg! When those tires wore out a year ago, I put on the 265's & it wentup to 11-13 mpg.

 

Your computer is still "learning" the new air/fuel curves and it will need some time to compensate for them. Usually within 500 miles you will be getting the most of the upgrade.

 

Also, you could be getting the "New Exhaust Foot" as I call it. Whenever someone gets a new exhaust system, they have a tendency to have a heavier foot than normal for a little while.

 

You should take it to the dealer and have them do an injector flush. they'll run it on a machine and flush the injectors runs a bout 150 or more i believe.

i have a 01 4.7 with 265/75/16 and get about 18mpg city. oh i use vavoline SAE30

 

FYI: When I first got it (new) in 2003, it was averaging around14-16 mpg with stock wheels & tires.A month after I got itI put on 275 75R 16 Radial Mud TA's, andit went down to 10-12 mpg! When those tires wore out a year ago, I put on the 265's & it wentup to 11-13 mpg.
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positive on the tire height..?i have a 02 i get about 11-14 in the city..this is what ive heard from others too... 265-70-16 single flomaster exhaust k&n filter not "cold air" jsut the filter in the stock box

 

I got have got the "new exhaust foot" too when I got my exhaust put on 2 years ago. it went away after about a year now I get 20-21mpg. I've smartend up alot since then too. (too many tickets)

If your letting your computer calculate it, then it could be off. I would fill up with gas and calculate it manually. it's alot more accurate.

 

you cld use seafoam to clean the injectors and carbon build up on the cylinders. I'm not sure what kind of effect it has on gas mileage, but it's worth a try. Throttle response will be better at least.

 

i have an 05 4.7 cc in my dak. when i first drove it was 20/22 on highway and 18/19 around town. then i put the 206 cams in it with the cat back and cai. now my mileage dropped a little 19/20 on highway and 16/17 around town, but around town evryone always wants to race. if i drive it normal i get about what stock did get. also if you changed out the plugs make sure you did not put a hot plug in. when i did my tune up, i put in autolites and my mileage dropped about 45/50 miles per tank. out with them an back to champion and wow what a difference. now truck has 30500 on it and still getting good mileage

 

also the other thing is you could have a clogged cat. this will screw up the system

 

Hey Guys,

I appreciate all the replies.

1st- I promise you that it's not a "Exhaust Foot" thing.
2nd- The injectors were flushed at the 36,000 mile service.
3rd- The tire size is/and alwayshas beencorrect.
4th- My calculations were all done manually (285 miles / 24 gallons =12 mpg).
5th- The plugs were changed at the 36,000 mile service. The guy said that they were the wrong plugs for my truck.

I'm seriously stumped here guys. I have friends with Full SizedRam Hemi's that get better gas mileage than me. And it's been that way since almost the beginning.

So what are my options?
- Clogged Cat?
- Computer malfunction?
- O2 Sensor?
- Still the wrong plugs?
- LEMON!!!
- ???

If I take it to DODGE, will they be able to tell what's wrong with it? Does the CAI & Magnaflow exhaust keep them from running the necessary test on it?