randallp84

OK everybody, my dream just came true last week and I am the proud owner of an 04.5 Quad Cab 4WD long bed 6-speed. It has the 325HP, 600 ft-lb HO motor. To my disgust, I drove about 400 miles home from the dealer and only got 13.8 MPG hand-calculated. My dad has an 03 6-speed long bed 2WD and he gets around 22MPG and my new truck doesn't seem to run near as good as his. I know for a fact that my truck can do much better on fuel and it's not running like it should. Now I know I probably won't ever get 22MPG out of it but I should be able to get AT LEAST 16. My brother suggested changing the fuel filter which I will do today or tomorrow. Does anybody have any other suggestions?

staarma

I would check to see if they changed the lift pump on the back of the fuel filter housing as well. Next, I would check the oil for level and also for diesel smell. Those two things will cause poor mileage. The fuel in oil will indicate a bad injector(s). Does it smoke at all? I have the same truck and with Winter fuel and a heavy foot I will get that kind of mileage you posted so it may be normal. Can't tell where you're from or what's done to the truck if anything. Fill in your signature and maybe we can get to the bottom of it.

lamadera

How many miles on the truck? How fast were you driving on the 400 mile trip? Stock tires/wheels, lift kit? I get a hand calculated 20 MPG on winter fuel on our weekly 300 mile round trip up north. That's 60-65 MPH, a bit of stop and go, not towing or hauling anything. Some idling to warm it up since we're at 9000 feet and it's been cold. That's the best I can get, which is great IMO. I've got the tires aired up to 70 lbs all around, and I've got stock tires. Truck is stock other than Timbrens.

Hounddog

As well as the above what gearing? 4.10 or 3.73.

randallp84

I checked the oil and the level is fine but I didn't smell it. No smoke that I can see, even when I lay my foot into it. I don't know if the lift pump has been changed and I don't even know what or where the lift pump is. I bought the truck in Oklahoma and I live in New Mexico. I filled it up in Wichita Falls, Texas. To be fair, I had a strong head wind all the way home driving 70-75. The truck is stock. Oh yeah, 3.73 gears. Stock-sized tires, no lift kit. 65k miles.

sqrl$$

I have 04.5 LB with auto and 33's. I only get around 13-13.5mpg on winter fuel. It picks up to around 15 in the summer. I would like better mileage, but can't complain alot seeing as it is my fault because of the bigger tires. Also check to see if any reflashes have been done to it. There was a reflash for poor fuel economy on that year truck. I was only getting about 12 before I have mine reflashed. I would check the condition of the fuel and air filters. Clogged filters = poor mileage. Also sounds funny, but check the air pressure in the tires. My tires now are only rated at 50 psi cold. I attribute this to alot of the poor mileage as the factory tires are rated at something like 80 psi. Low air pressure will definately kill mileage. Good luck hope any of this helps.

randallp84

I would like to add that even though I have never heard of a lift pump until now, I am by no means incompetent when it comes to the internal combustion engine or mechanical parts on a vehicle so don't be afraid to get technical.

ZachMI2003

Head wind and 70-75 mph makes my mileage go way way way down. I can ususally get around 18 hand calculated at 65-70 mph on summer fuel. I wish my mileage was better too. Somebody posted a few days ago to try putting an egg under the skinny pedal. Ha Ha

randallp84

Good suggestion, but I don't think that's the real problem because I have only had the pedal on the floor once or twice since I bought it.

randallp84

Hurry,somebody post to keep this thread at the top!

randallp84

Remember, I am also concerned about the sub-par performance. Will a new fuel filter fix this if it is plugged?

lamadera

Even with a head wind you should do better than that at 70-75 MPH. I get 15 MPG at 70 MPH with my slide-in camper loaded. The original lift pump is on the back of the fuel filter housing. If it's still there, I would replace it before it fails. Many fail right around your mileage. Do a search for options. BTW, the original lift pump can be bought now at Geno's Garage or Ebay for about $200.

staarma

A new fuel filter cetainly won't hurt considering you don't know the real history of the truck. The common rail lives or dies by filtration so it would be a good thing to do. The lift pump is mounted onto the back of the fuel filter housing literally. It is about 2" X 4" and has a fuel line running to it as well as a wire harness. You can't miss it. If it's not there then it has already gotten the updated one in the tank in which case for a stock truck will be fine. The filter mounted lift pump is suspect for sure. A fuel pressure gauge would be a grat investment along with a tranny temp gauge and EGT.

OOPS

One of the first things I do when I buy a used vehicle and do not know the history is to change ALL the fluids and filters. Peace of mind, I know what is in there since I am a Valvoline man.

TurboTed

Dump in a good dose of Howe's Meaner cleaner, and hook up to a load. Take it up some long hills, and work it a bit. I get 19mpg on winter fuel with an auto(highway), so maybe it needs a good workout.