I have a 1998 Ford 150 crewcab with the 5.4 i am getting about 11 miles to the gal. And that is on the highway I was hopeing i would get better than this.Is this about what i have to look forward to.

 

Has this been from day one? Just started happening? How many miles? Any mods?

I get an average of 15 mpg with city/hwy driving.

 

I just got the truck it has 64000 miles i put in a K&N air filter and changed the fuel filter.But the rest is all stock.

 

Try resetting the computer. You do this by disconnecting the NEG battery cable and then turn on the head lights (this just helps drain all residual power). Let it sit for about 15 minutes. Turn off the lights, reconnect the battery cable, start truck. Let it idle for a couple of minutes, and then drive it around. The computer will "learn" your driving style and adjust accordingly.

It may take 100 or more miles for the compter to fully adjust itself to you. Some WOT runs on the highway will help too, just watch out for the cops!!

Not saying this will help any, but it will at least get you a baseline to work from.

 

I don't think Ford made F-150 crew cabs in '98. Maybe you mean super cab (3rd door on the passenger side). If so, 11 mpg is not normal. Try resetting the computer like Mitch suggested or look for some other problem. Both of my 5.4's averaged around 15 mpg, the same as my 4.6.

 

I get 13-15 mpg. Depending on conditions. But I drive hard. See perticulars below.

 

I get between 10-11mpg in my 97 F250LD Supercab 5.4L. I am going to try the computer reset tomorrow. I got the truck about 3 months ago, 44,000 miles and running strong. I gained some mileage with the tonneau, haven't figured out the mpg since, but it was like 10.8-11.2mpg without it.

Any other suggestions? Will replacing the factory Y pipe help? I heard there is a restiction in it where the pipes meet.

 

Are you guys guessing the mileage are are you really checking it correctly????

Fill the gas to the neck and use it down over 300 miles and refill till you see gas in the neck...

11 on the highway is to low...check exhaust for clog-age.
check the air cleaner and maf..have the codes read..do you need a tune-up???plugs only good for 50000...

I had a 5.4 xtra cab w3.55 auto 97...got 16 -17 on the highway...

 

I would run out of gas before I hit 300 miles. My trucks gets between 10 and 14 mpg. 10 when I'm 4-Wheeling or burning rubber all over the place. 14 when I'm on an all day trip. 11 normal city driving which is mostly what I do. Lucky if I put on 5 miles a day. I try to take a 20 mile or so trip once a week. It's a '99 and has less than 17,000 miles on it.

BTW, it's not healthy to fill the gas until you can see it in the neck. It will get into the vent system and can overload the carbon canister. If I'm not mistaken, the manual says you should fill it until the automatic nozzle cuts off 2 or 3 times.

 

My 2000 Lariat 4x2 5.4L gets around 17 highway & 11-12 city. I
usually avg. 14-16 every fill up. You definitely need some heavy
diagnotics. Good luck!

 

Yes it is a crew cab i thought you could get 100,000 miles on the plugs.When should you change them.

 

Gosh, sounds like I need to try the computer reset also. My 2k 5.4 (all stock) is only getting 11 mpg in a mix of city/hwy consistantly. I've been tracking since new and now at 16,800 miles. Was blaming it on running Costco gas.

 

14.5 - 16 with 5.4 and 3.73s, 4x4, mostly city, if highway it's 80 mph, very heavy foot. All stock, always 85 octane. Can't complain I guess. I did get 11.5 once when towing 5000 lbs @ 7200 feet.

 

14city/17hwy

 

My worst tank was 7.12 MPG!!! That's with only the below modifications.