04 V10, 64000 miles. 325/65R18 (34"), above stock I know, but they are pretty much brand new.

 

Is 5mpg calculated with the tires factored in or not? Once you get the tank to a quarter put the seafoam in there then go fill up. I almost wonder if you have a sticking brake caliper or the hubs are locked in.

 

Damn. The only time I got 4 mpg was when I was down 3 coil packs. I average 10.3 with 285s and 4.30s now after tune up. You don't have any misses do you? Any loss of power at all? Or a fuel smell after shut down? Leaking injectors and bad packs/boots/plugs will net you crap mileage like this. I get 10 no matter what I do. Even pulling 15k I still get 10 and I've got 278k on the ticker. Keep us posted.

 

Mileage is calculated to accomodate for a 7% increase in tire size. I am pretty sure i don't have any misses (not sure what I would be listening for), but the truck idles fine and doesn't have "holes" in the rythm of the idle, it seems pretty consistent. As far as the brakes go I don't have anywhere safe (all parking is on hills) to really get the truck up and check the brakes. I am not noticing any funny smells or anything like that. Again it's only the second tank and I haven't filled it back up to do a true calculation this has all be rough estimates.

 

If you are using the fuel gauge to calculate your gas mileage, that is half of your problem.

 

I know, that's why I called them rough estimates. Filled the tank up today and those estimates weren't that far off. A little under 6 mpg is what my math produced. That's accounting for tire size.

 

Even though your tires are larger, you have the 4.30 gears which should still put you around the 3.73 range. And be better than 5-6 mpg.


Have you checked out the Washington chapter? there is a Spokane meet coming up, may be a time to tinker on the truck.

 

So I went ahead and ran a bottle of injector cleaner through the last tank. Same driving, I averaged 7.9 mpg for 3/4 tank. Went to the junk yard and bought a new airbox with the snorkel/intake hose attached and will put that on to see if that helps with air flow.

 

Gained 2mpg. That is pretty significant.

 

What did use for injector cleaner? For that big a bump from 5mpg I want to run some of that stuff! Lol. Seriously after you confirm the intake replacement mpg dump a bunch of that injector cleaner in multiple times if it made that big a difference.

 

8mpg is a little more into the city driving v10 territory, depending on how big the city and the stop and go.

 

I grabbed STP, in the black bottle.it was a two for one deal and it treated the right amount of gas. Very scientific I know.

 

I have used the seafoam through the tank and brake line vacuum hose with good results. Been trying techron and not sure if it does much.

That stp does sound like good stuff though.

 

That is insane. With 2" lift, 315 tires, 250k miles, pulling a loaded trailer around town I get 10mpg all the time. And 11-12 with out it. You need to check your coil packs. I was getting 8mpg when I was down 2 packs. Also with doin your calculations for your MPG. Fill the truck up all the way and reset your milage. Drive it for awhile, Fill it up again then take the distance you drove and divide it by the gallons of gas. There is no way your truck should be getting that. These trucks whether lifted or under load stay roughly the same.

 

I don't want to sound rude, but did you just tell me how to calculate milage?