How about 18.1 on the highway--i have a 4.6 / 3.55 / auto. All i have is a K*N filter and catback exhaust.

If your considering getting a v-6, you might as well get a 4.6. More power and that nice v-8 growl. Plus with a couple three mods, 20mpg is reachable

 

Hi to you too, Glenn!

Mitch

 

I don't understand the huge variation in mileage , and I know this subject has been visited much before, but for crying out loud I get 15 to 16 mps NO towing no 4wd no heavy loads not even a extcab i don't floor it. Only have 18k and it runs perfect. Like many have said it has no bottom end the auto tran likes to keep rpm ridiculously low, I'm sure a 5sp is better but very hard to find, [I also thought 5sp were not real rugged]. Anyway I know that if there is not enough torque at od rpm [65 mph sounds like 2200 to 2600 rpm , I don't have tach] It feels like itcan barely handle it esp. on slight incline. I know I'm rambling here, if I had a tach maybe I could use OD off button up to wwhat 60 65 mph, I have 3.55 and 255 tires thanks for any help Dan

 

I think there are a lot of factors, like how you drive and how you mod.

Some mods increase mpg, like FIPK, Cat Back, Tanneau cover, synthetics, lower axle and smaller tires. Some increase wind resistance like a bug shield, cab steps, over size tires and suspension lifts.

Some run reformulated gas in city/suburb stop and go traffic, while others run real gas down country roads where the stop signs don't turn red at the last second.

You can mod a truck for mpg and drive it for mpg, or mod and drive it the way you want to.

If you don't mod and drive for mpg the 5.4 has the biggest potential for lower gas milage. If you do mod for mpg the 4.6 has the biggest potential for higher gas milage. The 4.2 is bullet proof for gas milage.

 

Danjp, with auto and 255 tires you will be turning about 1700 rpm at 60. To explain my post some, my wife drove my 97 F-150 for three weeks when we were between vehicles ( had sold her's then bought an 98 Mustang). During this time the mileage dropped to 17.5 on two tanks of gas. She had to commute through a city and back to get to work. She usually had the auto shifting at close to 3k as i usually have it shifting around 1800-2000 rpm. I use cruise alot because we live in the sticks and I can sometiimes go a dozen or more miles of 55 without stopping. She also would wait until the last second to grind the brakes to a stop. Drives just like my brother to a tee. Location and driving style will make alot of difference. Now with electric fans, magnaflow XL muffler and open filter housing with a K&N stlye filter I am getting 21 to over 22 mpgs.Glenn Taylor.

 

Green_98 already commented on that quote about 4.6L owners not hitting 20mpg. For the record the best I have gotten in my truck was 21MPG on a highway trip about 3 months after I bought the truck. See my config. below. Granted my truck is not an X-cab or 4X4, plus at the time I still had the skinny 235 16" tires. If you are on the fence about a 4.6 vs. 4.2 then it's no contest. The 4.6L is well worth the small amount more it would cost when talking about the money you are already financing for the truck itself. Good Luck

-Brian

 

My mileage can vary quite a bit.
The biggest change I got over the board was cleaning the sensors in the intake tract. If you're super careful and watch what you're doing, this is a good routine maintenance bit.
My truck, a 99 shortbed regcab 4.2 5sp XL with 3.08 rear end and stock suspension height and tire size, rips. It's got 112,000+ miles on it and looks and runs like new. Passed a very restrictive smog test with flying colors. Very fun to drive and does the deed exceptionally well when needed to fulfill it's half ton truck duties.
On the highway, clear of bumper to bumper crap it's good for 21MPG. Driven like a go-cart in the city with my foot in the radiator it gets 14 or so MPG. Typically much better in the city if I'm not flogging it.
As far as the five speed and ruggedness goes, mine is doing great. It shifts like a truck. Most of the issues I've heard about it are folks complaining that it doesn't shift smoothly or get into gear very easily. That manual transmission aint like any sportcar gearbox for sure, mine is a little testy as far as lever effort goes, but not bad once you get into perspective. The F150 is not a mustang. It doesn't shift like one either.
The towing capacity is less with the five speed too, mainly because of the clutch. Not a very big one in diameter, the torque converter in the auto is rated for more.