I have been working on mpg stuff for a while, and here's some things I've discovered so far:
1. Install a fuel flow gauge, scangauge or similar gauge. Why? By watching the fuel flow against mph, or monitoring instant mpg you can see how your driving impacts mileage. The factory gauge is little help.
2. a CAI might help, if the original intake is really restrictive, but don't expect 2mpg from one.
3. free-flow muffler probably won't help, because the exhaust diameter is larger, meaning exhaust gas velocity actually decreases for the same given intake airflow at light throttle settings (when compared to your old muffler).
4. Superchips 91 tune can help, as it lets the PCM give more ignition advance. It is harder to keep your foot out of the throttle though!
5. Our trucks are heavy and have a terrible drag coefficient. Gears will probably help because it will be easier to move the truck. 4.10 is not much different from 3.92; most folks go with 4.56s... (I've not done this, but several folks have)
6. Efan will help a bit because it reduces the load taken off the crankshaft. An underdrive will also...
7. Tonneau covers help, as they reduce the truck's drag. See the RAM SRT10...
8. Weight reduction. The less weight you move the less fuel you use. Several interior pieces can be removed without much impact.
9. Don't expect miracles from a plug change, unless they'd not been touched in about 80k miles...by then they'd be so worn anything would make an improvment!
10. Synthetic fluids will help, but don't expect dramatic changes...

 

13.5 (a little more time on the HWY this tank) on the last tank of 89 octane. I filled up again today with 89. Yesterday I installed a CAI. I'm curious how that makes a difference.

 

so you think the cold air intake in the 4.7 is worth the money to improve mpg?

 

and if you have a 4.7 do you here a rattiling noise when you cold start? Mine make that noise, is this normal? I have heard it might be the hy time chain tensioner. get back to me if you could

 

Not sure yet... keep an eye on this thread and I'll let you know

 

I don't have a "rattling". I do have what I'd describe as "lifter noise". It did concern me for a long time, but I can't find anything wrong with the truck and I've heard enough "it's normal" comments that I've learned to sortof ignore it. I do check the oil on a regular basis just to be sure though.

 

ok thank you. I had that efan in my last truck it works great. The viper e fan fits right into the housing. just put a few bolts in it and done.

 

How many miles were on the 305's you replaced? If there were a lot and they were worn going to a new tire with lots of tread will drop your MPG. Did the 295's you bought have a similar tread or are they more aggressive than the 305's were? New/aggressive tread will hurt your MPG.

You may actually find that going to the 295 17's from your 305 20's increased overall weight not reduced it. The 17's will have more sidewall, plus they are LT's so more internal belts, so the tires will weigh more I bet.

Were the 20" rims you had the OE aluminum rims? They are actually pretty light. Did you go to a steel or aluminum 17" rim?

Post the tires you had and what you replaced them with and I can check the weight for you.

 

Both the old and new tires are Nitto Terra Grapplers. Yes the old ones had very little tread on them, especially compared to the new deep tread on these new tires.

The stock 20" rims were aluminum and the new ones are aluminum are as well. The new ones are "Ultra Wheels: Gauntlet (Matte Black) 17x9"

 

I have done nothing ex.. K&N air filter and cleaned my intake out. Also i changed my plugs to the champion platnium. My miliage went from 14.5 to avr of 18 mpg and 20's on the freeway with the 4.7, maybe to many mod's are A bad thing. part number 3071