i hav a 99 4x4 w/a 4.6 and ive talked to many ppl that hav had 4.6s and i got told they got 17 or 18 mpg..i get 12 and it disgusts my b/c i dnt even have a lot of pwr to compensate for the fuel mileage.. i did some rear end research and i was told they only put either 3.50 or 4.10 in those trucks.. is this tru? if so i think i have 3.50 gears and the engine is so lugged down its poor on fuel.. therefore i am tempted to spend upwards of 1000$ to get 4.10 gears but idk if itd give me the results i want.. expensive gamble.. has anyone else done anything like this w/ their 4.6?.... o btw i got a programmer and now get 14 or 15mpg but i still am not satisfied w/ the pwr vs mpg

 

You are getting 14 or 15 on the highway or city or mix?

I get about 12 MPG in town, about 15 on the highway (doing 75 on the interstate). I have a '97 F-150 4x4 with 4.6 and 3.73 gears. Outside of new upstream O2 sensors (other than the usual keeping it in tune, tire pressure, etc), I have not considered any upgrades for the sake of fuel mileage. I've read around here in some posts that replacing the O2s can help restore mileage... but I never paid much attention to the mileage when the truck was new.

$1000 investment to get, let's say, two miles more per gallon for me in the city would mean I'd have to drive about 28,000 miles to recoup that $1000 (assuming $3/gallon gas price). Unless my math is failing me, which it could be because it has been a long and tiring day.

Sorry, my post doesn't help you much.

 

that is mix.. ya you have a good point.. but at the same time lower gears will give me a little more pwr so maybe id be able to pull a trailer... but ya i just figured id see if anyone else has maybe done some upgrades

 

You need to be sure that the odometer is reading correctly. If you up-sized the tires then the speedo or the computer has no real idea how fast the truck is going. This can effect many things b/c the PCM controlls so much based in the input it gets from ALL the sensors, VSS included.
Just a thought!

 

yeah im only getting 13.5 average for my commute its a fairly trecherous 70 mile round trip drive. downhill with a back wind averaging about 60mph (the wind) but on the way home its climbing 3000 feet with a 60 mph headwind.. i was all stock when i got it then i did exhaust intake and a hypercrap tuner and i got zero mileage improvement just a little bit better driveablity (very little). if i go on flat-ish highway i never did the math but im gunna guess 17-19 mpg and thats at the speed limit. if you really wanna improve your mileage the secret is to keep it under 2000 RPM i guarantee you get big improvements, just my drive doesnt allow that. GL

 

When I got my truck in may, it was bone stock, 255/75/16 tires, everything. I got on average 16-17mpg city, on a long trip I calculated at between 19-21mpg highway set to cruise at 68mph. I now get roughly 14.5-15mpg city with 295/75/16 tires and 17-19.5 highway, depending on how I drive, calculated on the gps. The harder you drive the truck the worse your mileage is. Like said before, keep it under 2k rpm and your mileage will go up considerably. Hope this helps.

- B