I have a 2006 F150 5.4 V8
I use to get about 22 mpg. Over 500 miles on a tank.
I have put on:
dual exhaust just behind the cat
K&N intake
Programmer (set to economy)
Now I am lucky to get 16 mpg and maybe 300 miles if I run it to E. Why is my milage crapped out? How can I fix it? I took it to the dealership and they say everything is fine. Anyone else I talk to just says "huh thats weird"
So any ideas?
Thanks

 

Can't help ya, but I have never seen over 15 mpg!

 

You should appreciate the 16 mpg. Most I have heard about is an average of 12-14.

 

Have you ever replaced the fuel filter? Although 22 mpg is pretty incredible and 16 seems pretty normal it could be that your fuel filter is just in need of changing.

 

Mine is also 2 wheel drive. The 16 mpg is on the freeway with cruise. I've been getting about 12/13 in the city.
I'll have a look at the fuel filter and double check when it was changed last.

 

air filter, fuel filter, pcv valve, plugs and wires, o2 sensor, tires properly inflated, same driving style, oil filter and fresh oil. Thats about the totality of my advice. Anything past those suggestions i have no idea about.

 

You didn't say how many miles the truck has or gears or what hind of programmer. Are u running canned tunes or custom tunes. If you are running the tunes that came with the programmer (canned) it might not be set to run a CAI. That would throw off your A/F ratio and give you a drop in mpg. It's possible that an injector or two are going bad. I would re-install the stock air filter system and see what the effect on mileage is. If it's the same, I'd remove the programmer and return the PCM back to stock and check mpg. If it's still down, you have an injector or other problem with the truck. Some things that can decrease fuel mileage on a stock truck are retarded ignition timing, cam timing that's out of spec, poor state of tune on the engine, or possibly even transmission problems. I hope this helps.

 

I'm not sure what programmer you're running but what was said above is absolutely correct. The tuner may not be running correctly with the CAI. I know with the Edge they suggest custom tunes if you have a CAI because it could run too lean.

 

when I bought my 04 FX4 i was getting 18-19mpg and once i hit 65k it dropped to 16mpg and was never able to get 18 ever again. i have replaced lots of parts just trying Good luck

 

I have a little over 53,000 miles. The programmer is a Edge Evolution.
I have been pretty sheltered when it comes to mechanics. What is CAI? But I have set it back to stock to see what would happened and the mpg is about 1 less so 11/12 city.
I did the full 50,000 mile tune up at the dealership. They say it's fine.

 

CAI (Cold air intake) = your K&N, it's important to note these trucks are very sensitive to changes in the intake, I'd put the original back on.

 

Well being the genius that I am I got rid of the stock intake. 04-08 should fit right?

 

04-08 should fit. Another option that u have is to send your Edge Evo to Power Hungry Performance (one of our site sponsors) and have Bill convert it to a Gryphon tuner with custom tunes. He can set your Edge programmer up to account for the CAI and get a lot of your MPG back if not all.

 

I am not a mechanic but every truck I have owned lost mpg's right after adding an exhaust and i believe that the problem is your right foot

 

For what it's worth, I've read on here in the past that the K&N filter can cause the mass air sensor to get fouled with oil. I can belive that under the right conditions (nice level roads) and all hiway driving, no head winds, that you can get 22 mpg, especially on a 2wd truck. I've gotten 18 once on a trip in my 4wd but average 16 or so around where I live.