I've got a 2003 F150 4x4 with a 5.4 36,000 miles k&N intake A couple months ago I was getting 14ish normal driving and 17ish highway. For the last 2 months I've been getting 10 normal driving, 13 highway. It still runs good, no warning lights or anything. Any suggestions as to whats going on? I called the dealer they said there's nothing they can do. I've had problems with the rear axle (limit slip not working) and front axle ( shifting fork not working) could eith of these be the problem again? It seems like all of a sudden I'm getting bad milage. One thing I need to do is change the fuel filter.

 

I have a 2002 F150 4x4 with a 4.6, and I've NEVER gotten 17-ish on the highway, and this is the 3rd 4.6 I've owned. Are you actually dividing miles by gallons used, or just making a gas-guage estimate?

They ALWAYS get worse mileage in the winter, but if yours is actually measuring 10, I'd say that's kinda low. 13 sounds normal. Fuel filter will have zero effect if it's running well at high rpm; if it's flowing enough fuel then, a new filter isn't going to make it get better mileage.

Mine is getting 12-14 city/highway actual mileage right now, which I don't like, but I've made peace with.

 

What part of the country you live in? If you are in winter driving like I am in ND, that's normal. Normal temps are in the low 20's, but we can get to -20 below also. So mileage right there sucks.

Also, depending on what part of the country you are in, your gas stations may have switched from pure gasoline, to ethanol blend. In my area, I use 10% ethanol all the time. I notice no difference in my truck. But I've read others having issues.

 

I pulled a trailer with 2 quads on a 600 mile trip last month and averaged 9mpg. I'm thinking somethings wrong but maybe thats the way it is. It's an occasional driver and I get reminded why everytime I figure my milage. Thank You for your reply's

 

Winter gas would be my guess...

 

Some gas stations are adding 10% ethanol in their ground tanks now.

that will kill your milage. Have you installed a new air filter lately.

 

The ethanol mix should only do 10% difference in fuel-eco 2mpg at most?

 

It's cold out now, I have the same issue every winter. Right now it is -10F here and I don't expect to get much more than 10 mpg.

 

That's exactly right I was getting 10.5 mpg pulling a 4300lb camper two years ago. This last summer pulling I got 8 to 8.5 mpg. I noticed all of the stations on the trip had yellow signs hanging at the pumps stating a 10% ethanol mix.

 

It must be the weather and ethynol combination. I'm in Michigan and we're right in the heart of winter. As far as the air cleaner, I just put the K&N on so it's clean. I was hoping the K&N would help but it didn't.

 

Are the new 1/2 tons better on gas?

 

They say the new ones do. but probably a lower horse power engine.
My Truck has the 5.4 280 HP. never over 14mpg on the high way brand new.
I sold a same year Econoline with the 5.4 220 HP and I go almost 19mpg going to Colorado one year and never got under 17mpg with it the 4 years I owned it.
I've had my truck almost 8 years and it's a good one but it never gave me a break on drinking gas.

 

Has anyone tried burning hiher octane gas? Would you see an increase in milage burning 89 or higher octane?

 

Just throwing this out for what its worth and start by telling you up front I have a vested interest in ethanol however I messed with blends in my truck because of the cheapness to 35% ethanol before I have had any mileage issues in my 4.6 2000 4*4 super cab. Hauling wheelers I do not do good on gas and when I load the 700 artic cat in the back which doesnt hardly fit I can definately tell mileage wise. One thing that I would throw out is have you checked the MAF I quit running the KanN because it messed with that(oil) once I quit I do not see that issue I was having and my mileage took a beaten for it. My younger brother, dad, and a few cousins cover the years 97-03 with fords and all have had that experience just a thought. I am not sure what I did wrong with my KN as I know a lot of guys who run them including my brother and my father and do not have issues. I like to drive it like I stole it.

 

All I know about ethanol is that it has caused the gas mileage in everything I own to go down!

My lawnmower used to use a 1/2 tank of gasoline to cut my 2 acres. Now it uses 3/4! Maintenane is kept up on this as is all my vehicles.

My 4.6 auto used to average 16 mpg in town and I could get 21 to 22 on the interstate...not anymore! Mileage has dropped to 14/15 in town, 19 on the highway. It started this ever since they started adding ethanol.

My wife's new 08 Explorer with a V6 averaged 22 mpg highway when she first got it and it now averages 19.

This is not just my opinion around here where I live!