I don't profess to know it all, and I'm obviously not setup anywhere close to where I will see good gas mileage. I have my pig weighing over 1500 lbs. heavier than a stock setup. But...

I read post after post about guys claiming like 5 mpg gains just by adding a CAI. Won't happen. As stated, cold air is more dense, it makes more power by virtue of more fuel being dumped into it. I don't know how guys are making such claims and being so indignant when others doubt them. But the physics of an internal combustion engine makes it dump more fuel into more dense (cooler) air. By contrast, introducing hotter air into the throttle body increases fuel economy, by leaning the A/F ratio, albeit while making LESS power.

Now, that said, a CAI can benefit other mods to make them work more efficiently and result in an overall mpg gain. CAIs make headers and cat-back exhaust able to scavenge more efficiently. The better you scavenge exhaust gases, the less your engine has to work to push out spent gases. The result is both more power AND better fuel economy.

Now, you can see a MPG increase by adding power by virtue of the fact you can achieve the same speed with less throttle, but you'll never see a MPG gains that would be cost effective for what you spend on mods. Plus, for most people, more power means more throttle pressure.

If you are looking for more MPG and KNOW FOR A FACT others with a similar setup (same engine, etc.) are seeing significantly better mileage than you are then common sense says you either have an issue with the truck (bad component), have neglected maintenance on some front, or your driving habits are just very poor.

Could be a previous owner just dogged the thing and you have issues common to a dogged engine. Internal valve seals, loss of compression, etc.

No amount of modifications you make will get back fuel economy if some other factor is making it poorer than most trucks with similar setups unless by chance the mod replaced the component(s) causing the issue.

After the basics (tune up/synthetic fluids/fresh filters/air pressure in tires checked, etc.) about the only modification that will give enough of a MPG increase to warrant it's cost IMO would be an efan.

The 4.7 is a good V8, if properly taken care of it has a good history of longevity. I personally know two guys with over 225,000 miles on theirs, one a Grand Cherokee owner and the other a Dakota owner. BUT in a full size pickup, I don't know of anyone getting any better fuel economy than a Hemi in a similar truck setup. The larger displacement engine simply does not work as hard to move the weight.

 

Ok, I do have the efan too, I guess I will try the factory air box and see if that helps any.

Do you think lower gears would help?

The truck shows no cells so how would I figure out if there is a bad sensor somewhere causing the problem? I replaced the AIT sensor thinking it was a problem but no change and it was filthy. Cleaned throttle body, and Checked throttle position sensor.

Any suggestions where to start this thing HAS to get better mileage and I intend to figure out why it won't!!

 

girlfriends brother has a '02 quad cab 4.7 two wheel drive with about 115k miles. 20 mpg hiway and about 15 average both city / hiway. no real mods to speak of. there is no way you should be worse with a reg cab.

i had a megacab hemi 4 wheel drive that got about what you are getting with your reg cab 4.7.

 

Hammer,
You said something about previous owner ******* it. What do you mean?
Like it is clogged up and maybe the cat is partially clogged and needs replaced or cleaned out. Replaced the plugs ran some seafoam through the best that usually cleans em out good, but no change either this thing has to have something choking it to get so poor mileage. I guess the cat may be next on my list of un choking it, by the way looking inside with camera and the thing looks clean inside. Friend had access to one of those flexable cameras they are so cool..

 

I'm not Merriam Webster or wiki, but I'll do my best.
Definition of *******--------------------------------
1 a: To Dog on a vehicle; Thrash, tear rubber, kick sideways,
b: To have been ragged on, pedal to the metal, drive it like you stole it
2 a: never changed oil, ran oil low, neglected maintenance until tow...etc

 

I don't think it was ragged on, I know the original only other owner of the truck he drives them but does not neglect them or drive em real hard. I was talking to him about the mileage and he said "that is why I got rid of it" He says somewhere around 50k it started getting worse and worse mileage until he decided it was time for a new truck..
So with that in mind I am thinking an O2 sensor or cat is bad, starting to lean towards the O2 sensor cause my tailpipes are dark. Probably have killed the cat too, with a overly rich fuel load.

 

If either of those are the issue, would the engine light come on?

 

I have been told they can be out of spec and still not throw a code due to the built in variance in the computer for changes in sensors over time.. but I to thought it should throw a code if something is wrong with the truck. So what ever it is, is very close to good so as not to set off a code in the computer..

 

Well that just sucks. I was getting 8-9mpg when i had on my 12.5x35 nittos. Got rid of them and went to stock size. (33's) Got a CAI with an exhaust and i do drive like grandpa and i dont romp on it. Im getting 10.5mpg now. And Ive cleaned the throttle body. Im not asking for prius numbers but 10.5??

 

I am glad I am not the only one that feels 10-12 mpg is unacceptable out of a fuel injected motor. Do like I did and take the CAI off, put the stocker back it helped get 1 mpg back so far. I think these motors are really choked in the exhaust. I am thinking of removeing the guts of the cat. Since Ks does not do inspections of any kind. A visual for the ocassional state trooper stop will be good enough..