ok,

new vp44, airdog II, edge juice with attitude, 4" from turbo all the way back.
all these things have not helped my milage AT ALL my tires are 234/85s not sure if these are much biggedr then stock but i think they are. because when i am doing 70 on highway my gps says that im doing 77 mph. when i calculate on paper miles divided by gallons. i get 12-13 mpg. when i tow my 33' fifth wheel i get 10. this seems to be terrible! is it because of the speedo off due to possibly biger timers? my friend has exact same truck littel bigger exhaust same edge system but he has bigger turbo and injectors. even with that he drives like a bat out of hell with his 38' fifth wheel and still gets 14-16. any help at all this drives me crazy. i just put some lucas oil fuel conditioner in to see if that helps.

 

First step is to confirm accuracy of odometer. If your GPS consistently indicates that you're going 10% faster than the speedo, you may be getting 10% more mileage. Are you hand calculating or relying on the computer? I get 16 mpg with 410 gears & a NV 4500.

 

don't lug the motor. I have noticed over the past 3 weeks, that driving w/rpms @ 1700 vs. 1500 or 1600 has increased my mileage by 2+. At least this is really the only thing I can think of unless going from level 1 -to- level 2 on the Adrenaline had significantly changed timing/fuel. I thought it was due to summer fuel blend being mixed in but others stated no summer fuel in Tx.

 

yeah, problem is i have a dually and the gearing is low. (i think 4.10's) and at 60 mph i am running around 2000 rpm. my tires are 235/85's so i think this is bigger then stock which explains the speedo off. i think that might be the problem.

 

The diff ratio doesn't help if you want to run 70+ mph. Stock tire is a 215/85/16 which would turn more rpm than now, should be a sticker on drivers door to confirm. A suggestion would be going to a 255/85/16 to lower rpms or just slow down which is cheaper.

Use this for reference:
http://www.miata.net/garage/tirecalc.html

HTH.

 

I run 35's on my dually and my 91' because they both have 4.10's and I get roughly 2 mpg better on interstate trips because of the bigger tires, so overall the better mileage offsets the extra cost of the tires... and I have to admit I like the way it looks too.

FTW: I don't think your mileage is that far off, for my dually the best mileage I have ever gotten was empty on flat ground never going above 50 mph for long periods of time, and I got 22 mpg, worst I have ever gotten was 8 mpg pulling 12k, and average is about 13-16, and I don't drive easily.

 

how many miles are on your truck right now?

 

Have you checked your apps? Any codes?

 

410 gears work against mileage as does dually and 4x4 but you have what you have.

You can check mechanical issues all day. You don't know whether you have a problem or not until you confirm the accuracy of the odometer and hand calculate mileage through several fill ups. I think that odometer can be recalibrated by the dealer. Dealer can also confirm what rear end and ratios you have if given the VIN.

 

find a rear with 3.55 s it will up you to the 18+ mpg area 4:10 are killing you