When I decided to buy this truck it was really because the dealer is reputable and the truck looked super clean. Every detail was as to be expected. I am not an expert in buying vehicles which is why I went to a dealer. During the test drive, the truck handled well and everything seemed normal. After driving it for 3 weeks, I am concerned with a couple of things:
1) the truck seems a bit under powered under normal driving conditions.
2) the mileage is absolutely terrible on it, even while expecting bad mileage, I am still surprised by it. Under 10 mpg.
There are no codes showing on it and I honestly don't know where to begin. I don't want to find out that I made a mistake with this truck especially after deciding not to get the extended warranty.
I am not afraid to do things myself but I am not a fan of throwing parts at the truck until the problem is fixed. I am not rich by any means. If I was, I would have probably got a 4x4 diesel" but that's another story.

The truck did originally have a small leak in the vacuum line (p0456) but a new gas cap seems to have fixed the problem. I was hoping the mileage would improve as a result also but not so.

Any insight on this would be greatly appreciated. Thank you all.

Ps: the truck is an 03 ram quad cab 4.7L 4x2

 

1) It's a non HO 4.7 powered 5300lb truck.
2) See #1

The 2 biggest things you can probably do to pep it up a bit and possibly (though not likely) gain a little bit of mileage is to get a programmer and put 4.56 rear gears in. Keep in mind, this is the smallest of the 3 available V-8's that year. I am sure the guys with 4.7's will chime in here for some additional questions/suggestions.

 

Have you tried cleaning the tb also a dirty egr will make your mpg bad

 

i've been driving my father-in-laws 2005 quad cab 4.7 for the past few months. dealership where i been for six years as a dodge mechanic went under and i sold my mega cab so we could keep our trailer.
the truck got really poor mileage when i started driving it, like right around where i was getting with a mega 4x4.
cleaned the tb, egr, cleaned pcv, gave it fresh plugs- the plugs were terrible btw, filters and a full seafoam treatment and the truck went from getting about 12 mpg over all to right about 16. on a trip from alabama to tennessee last weekend it got about 18 mostly highway. i can't complain.

 

Thanks for the help guys. Another thing that I forgot to mention is that while I'm driving on a straight level road and I shift the automatic trans to manual to coast, I notice that the RPM shoots to almost 2K and then drops to around 500 and it keeps doing that over and over. Not sure what would cause that to happen. I didn't notice a rough idle while at stops but I will keep a closer eye on it.

 

That sounds like the IAC valve. Idle Air Control.