Just bought a 2005 F150 Crew Cab 5.4 4X4

3" Lift, 35" Tires, Fender Flares, Edge CS Fuel Programer, Volant CAI, 155Kms.

My speedo is out about 20 kms/hr when Im reading 80kms/hr (really doing 100).

I know the big difference in tire size is to blame and I hear I can get it recalibrated.

I filled this bitch with fuel Saturday for about $100.00. My trip meter is reading 120kms since fill (will be out a bit with tires) and Im below 3/4 nearly at 1/2 tank. I also own a 04 Hemi (6" lift) but don't think that trucks (5.7L) as bad as this f n thing. Holly

 

Do you have an actual hand calculated figure? Dollars in the tank divided by what the gauge says is meaningless. I have an 05 FX4 5.4L supercab/6.5' with tires that measure 11" by 33"dia. and 3.73 gears. It has a 2" front leveling kit. Cruising at 55-60 mph I get a true 16 mpg. Sorry its not in Km/L. but its a reference.
Frankly, considering its lifted with big tires and programmed, I'm not too surprised that its a bit of a pig. Unfortunately that happens pretty fast with those types of mods. Been there done that!

 

Pay to lift em and then pay to drive em. Mileage will suck.

 

5.4L F150's aren't the greatest on fuel mileage to start with. When u add taller tires with a lift without changing the gear ratio fuel mileage does go down. If you are running 3.55 gears that will be even worse because you are lugging the engine even more. It needs to be in the proper rpm range to be at its best. On the 5.4L engine, that sweet spot is 1800-2200 rpm. Below 1600 rpm you are working the engine much harder because you are running below the power band it was designed to run in. My '06 with 3.55 gears & stock tire size was doing 1700 rpm at 105 km/hr which equals 65 mph. I know that truck would have gotten better fuel mileage with 3.73 gears, especially towing.

 

I can only assume my gears are stock, as the pot doesn't appear to be opened.

The manual is pretty long on this programmer I have, but its that what its designed to help with ? Taller tires, fuel milage ?

 

The tire size you running would amount to you running a 3.0 gear ratio if you have 3.55 gears. That would make your rpm @ 65mph(104 km/hr) be around 1480 rpm which is at least 100 rpm below the lowest rpm where the engine likes to run. So you would be lugging the engine and putting strain on the transmission. I can't answer about the programmer. But the only thing you would be able to correct would be the speedometer and odometer readings by changing the tire size in the PCM with the programmer if it has that feature. It will not change the rpm range that you need to run for efficiency and power. That can only be accomplished by changing the gear ratio to 4.10 or 4.30 to correct the rpm range that the engine runs in with that size tire. The same thing can be accomplished for less money by putting the correct OEM tire size back on. My '06 XLT EC 4x4 with 3.55 gears and OEM tire size got 17.0 mpg on the highway and 15.4 mpg mixed driving. I can't say what mpg it would get in city driving as I never ran all city miles on it. On the highway with the 36 gallon tank I could get 400 miles (645 km) at the 1/4 tank level on the fuel gage. I would put in 23-24 gallons US to fill it. This should give you a reference point to go on.