invest in a vacuum gauge, and make sure you keep the needle in the green, that will help some. other than that, check/fix your plenum, get rid of the death flash with an sct tuner. its pretty hard to improve gas milage in these pigs without spending a crap load of cash. replace your gears, go with 4.10's or better that will help a bit. good luck with it. if youre gettin 11-12 consider yourself lucky! i get 9 on a good day, but i gotta fix my plenum!

 

Don't forget make sure your tires are properly inflated. That helps as well.

 

sweet picture by the way haha and thanks!

 

i've got a third gen QC 4x4, running 5.9L Magnum w/ 35"x12.5" tires, and I'm getting 13.5MPG overall mileage over the past five or so tanks.. I live on flat lands, and that has a lot to do with it, but here is my thoughts on the subject, and I ranked them just for the hell of it:

1. drive sensibly
2. properly tuned, including PCM, plenum gasket fixed, air filter, plugs. wires. caps. rotor button. coil. catalytic converter, clean TB and all sensors especially o2 sensors..
3. e-fans
4. gears (4.56:1 on mine)
5. vacuum gauge is awesome to keep from unnecessarily loading engine
6. tire pressure maxed out
7. DON'T use o/d in city
8. use only good gas
9. relocate your IAT sensor to your air hat
10. headers/ less restrictive exhaust

the only thing i've done to harm mileage is the 1.7rr's.. I'm confident I could get 16mpg on highway in this pig, but I've not stretched out any hauls to prove that yet..

you can dump excessive weight from the truck to help you out, like crap from the cab and bed you have but don't need.. You can run lighter and more narrow tires.. that would net you as much as a couple MPG's.. remember, rotational weight is weight x4.. if your wheel tire set up weighs 100lbs, (mine are 140ea), you're running equiv of 400lbs on each hub.. that makes a difference.. if you can half that (good luck) you could easily increase economy up to 2~3MPG's or so..

there is a point though, where you just have to accept what you got- a vehicle designed to haul/tow/work.. and 12~15 is a good range for them.

 

there are lots of ways to make any vehicle more fuel efficient but it costs lots of $$$$$$$$$$$$

 

Don't go to any extremes. Do all the proper maintenance. Plugs, wires etc. One thing that is overlooked is cleaning injectors and intake. I use Lucas Fuel Injector Lube/cleaner/stabilizer. Get the 1 quart bottle, better buy. Then you can take the air filter housing off and clean out the throttle body and spray the heck out of the intake that way. You can buy or make a vacuum feed tool and run sea foam through the vacuum lines. Don't max tires out when doing a cold check. Anything over 40psi won't help any. The key is keeping the tires from getting below 35. Beyond this there is not really anything you can do to improve fuel mileage on the 5.9l magnum.

 

My spark plug wires look good still, does that matter or is it a good idea to replace anyway? My spark plugs look good too and have the correct gap. I don't know how to check the cap and rotor though or how to tell if it is bad or not. My truck does not have a problem starting though.

 

just because the plug wires look fine doesnt mean anything. mine look perfect, other that the typical grime and grease under the hood of any vehicle. when it rains outside my truck will not start. any type of damp weather does my truck in. i got lucky today, i started my truck twice over night to make sure it would start for me this morning when i leave for work. a good way to check to see if they are good or not is...wait til it gets dark out, open your hood unplug the under hood light, and start your truck. let it run for a couple minutes and then take some windex, or any glass cleaner and spray all the plug wires, and watch for sparks, or listen for a miss in the engine/rpm jump. if you see sparks its time to change them, and you should change the plugs at the same time as well. if you just bought the truck, its always a good thing to do a complete tune-up as soon as you get it home, because you dont know when the last tune-up was done.

goodluck with it, hope your gas milage improvement works!!

 

well i just made a thread on how to improve gas milage...so you didnt search hard enough.


i just spent a little under $200 for some things, and it brought my mpgs up from 8 mpg to 12.2 mpg....and i have 208,xxx miles

all i did was

-timing chain
-harmonic balancer
-hollow the CAT
-Cherry bomb turbo muffler.



but i also have 4.10 gears wih 265 tires....ive fixed my plenum etc.....and i also have about 7K invested in new parts into the truck


All in all the best way to get the bes mpgs would be this IMO


-Plenum
-Timing chain
-Swap for D60 axles with 4.10 gears
-Convert to manual lockin hubs on axles, so theres less parts the truck has to move
-Electric Fans
-Dump any access weight
-Get a new CAT
-New 02 sensors
-full tune up



i guarentee you'll boost up at least 6 mpgs by doing all those...but ye it will be expensive......if you dont like the mpgs, you shouldnt have bought a truck......Trucks arent made to get 40 mpgs.