So two weeks ago i bought a 2004 slt 2500 5.7 quad cab.
this truck has approx 120k miles on it.
after i was 3/4 of the way through my first tank i filled up and did the math real quick and was astonished to see i was getting 7 1/2 mpg!!!
i had allready poured a bottle of prestone injector cleaner in with the first fill up.
so i headed for the parts store and picked up new plugs, a bottle of lucas oil stabilizer (i noticed the oil was about a quart low) and a bottle of lucas's tune up in a bottle. the plugs call for a .045 gap and all 8 i removed were between .055 and .059 so definately worn.
i think this has helped some allready but too early to tell for sure.

SO I AM HERE TO ASK.... what all can i do to improve my mpg???????

ive heard tornadoes work and also that changing rear end oil and tranny oil to full synthetic helps as well???

should i change my o2 sensors?? if so which ones? thanks guys!

 

Welcome to the site

Lots of things in our FAQs that can help.

https://dodgeforum.com/forum/3rd-gen...0&daysprune=-1

Proper tire pressure, good spark plugs and wires, good clean air filter, try to find and use non-ethanol fuels, lighter smaller tires/rims, with 120k on it you should have already changed your trans and rear oils a few times, a good tuner can help out also, replacing the EGR might help, cleaning the throttle body and you can replace the front O2's

 

since it was used im not sure what the owner did as far as maintenance! i pulled a car fax and its a clean 1 owner. bout all i know.
the air filter is brand new ill chack tire press but im sure its very close.
can the plug wires really have a noticeable effect on mpg?
and if i do change the tranny and rear end oils should i go synthetic?

 

When in doubt, change it out.

The trans already has synthetic in it. Most guys do swap over to synth for the engine and rear end though

 

FULL tune-up and I mean a complete one, clean the throttle body (huge MPG robber is a dirty TB), all synthetic fluids, run tires at 80% of max cold PSI, run 89 octane fuel.

O2 sensors would be popping a CEL if they were out of spec, so I wouldn't change them. The Tornado is a joke, won't do a thing.

 

thanx fella's everything sounds great ill be checking this stuff off one by one.
and for the newby question......
how exactly would i go about cleaning the TB??
does it have to come off?
will the build up (dirt) be visible from atop the engine?
ive never messed with them so although im fairly mechanicly sound its one thing thats escaped my learning!
thanks again for any and ALL help!

 

https://dodgeforum.com/forum/3rd-gen...y-hemivec.html

 

Change the other eight plugs - a TB clean and a Sea Foam dose might be in order.

 

thanks for all the help so far!!
i did end up changing the other 8 plugs yesterday before i took an hour drive south to indy, according to the onboard mileage comp i was getting about 12.8 or so on the highway at 65 mph. got up to about 13.5 at times mainly when following trucks.
and thanks for the link on the TB cleaning! ill be doing that sat or sun, and hopefully that helps me out too because i cant afford to keep this truck if i cant get my mpg up at least a few.
i need at least 11 or 12 in town and i cant believe i couldnt hit 14 or 15 on the highway.

anyone else here with a 2004 2500 slt 4 door 5.7 that can tell me if theyre getting better than me? i think right now im getting about 9 in town. thats up from 7.5 after the new plugs

 

Never trust the OHD calculations. Always do you MPG calculations by hand