Moore08

Thanks for all the answers guys .. I was thinking it was the plugs as it just recently within the past week started doing it. .. I'll be taking it to the dealer Monday and try to get a new catalytic converter since my truck throws a converter out of efficiency code ... My truck still falls under the power train warranty and my dealer charges 95$ every time they hook a computer up if the check engine light ain't on .. My check engine light will come on then go off which I think is a bunch of crock because I know something is up with the converters

brucesears

Crap, I get 14-15 pulling my 4K boat at 70 down the interstate.

maplelakeduckslayer

Ecopoop- you have tow mirrors?

My mpg plummets at 75 mph...14-15 mpg at that speed. There are conflicting opinions on the tow mirrors, but I really believe at fast speeds(75-80 mph) these mirrors do affect mpg substantially. One of these days I am going to do a back to back test at 75 mph+ for 20-30 miles and see what happens. Just judging by the terrible wind noise in my truck at those speeds...I think the mirrors affect it. Since I can get 22 mpg at 65 mph...I know it is running pretty good. Don't know what else it could be. Obviously my truck is about the worst config for mileage. I don't expect 20+ in my truck at 75...but consistently 16-18 would be nice. No one should expect awesome mpg at 75-80 mph.

EcoPoopFX4

No, just standard mirrors. my truck has gotten this crap mileage since day 1 off the lot. I might consider trying to change the plugs, but I dont see how it could be that since its been doing it from the beginning. Texas hwy speeds are 75 and I aint going 65-70

SkiSmuggs

It is hard to believe after 3 years, Ford still hasn't given the techs a list of things to check for poor mileage. It is still "if there are no codes, there is nothing we can do" as opposed to "there are some things we can check, bring it in."
My biggest worry would be an injector pumping too much fuel, washing the cylinder walls and causing a failure.

boosted150

When you say "filter swap" do you mean air filter?

I tried a K&N drop in on my ecoboost, and lost 1.5mpg consistently over a 6 month time period. Zero power gain and lower mpg. I put the stock Motorcraft paper filter back in, and got my MPG back. Try that if you have a different filter.

Also, take a look at the plethora of MPG threads on here. There are many, many variables, but a few to look at:
1)Tire pressure. Mine are all at +2-3psi vs what Ford wants them at (all 37-38psi). Some run more psi like 40, but you run the risk of uneven tread wear on the tires.
2)Leveling or lifting. Don't do it if you're looking for MPG
3)Rear end. 3.15 will give you better MPG than 3.73 or 4.10 (yours is 3.73 I believe, so you're not going to get as good of mileage)
4)Gas company. Use higher grade gasoline instead of 'bargain bin' gas stations (use Shell, Texaco, BP, etc). Some say octane can also make a difference. I've noticed that running 93 octane makes the engine run smoother... no more miss/shudder at 55-60mph
5)Spark plugs like mentioned above. If your gap is way off (and a lot of them are from the factory) you will run inefficiently
6)Driving style. If you floor it at every light, and slam on the brakes (instead of doing some coasting) at stop signs/lights, you're going to waste gas.
7)4x4. You're turning 2 axles instead of one. 4x2 will always get better mileage.
There's more, just search the threads.

BlueFlameMetallicFX4

Well, what was the fix? Mine just started missing at full throttle...I'm going to try and install Denso Iridiums. I've had great success with them in the past.

SkiSmuggs

Get the Brisk Silver Racing plugs instead. Every one is posting good results with those. The stock plugs are Iridiums.

BlueFlameMetallicFX4

Just curious, what's the difference between plugs?

I'm on their site and it does not show a part number for the ecoboost...any idea?

SkiSmuggs

BRISK Silver Racing RR15YS is the stock heat range. I think the 14 is one step colder.