Bought a 2010 F150 supercrew w cap. Has 45,000 miles on it. Put a K and N filter in it, and treated it w BG44.(gas additive for those who don't know). Has 285/70r17 tires. I'm getting 10.4 mpg in city. I drive it like a Granny. It is the 5.4 engine. Is 10.4 mpg acceptable? I haven't taken a trip w it, so I don't know about highway mpg.

 

K&N filter will do nothing as has been posted many times, and gas treatment is not needed or recommended by Ford.

10.4 is low.

 

Not knowing if it is 4x4, tires, or what the rear gears are I would be guessing. For city driving I inflate my tires 1.5 pounds more than the door says.
I have a 2011 ecoboost and a few hills and red lights I can drop down into this range easily.

 

 

Not in the slightest.

 

There is nothing you can add to the truck that will improve fuel mileage enough to pay for what you added. There could be some things that you could remove that may help. You wasted money on the K&N filter. Not only do they not improve performance on most vehicles they don't protect the engine very well. I'd go back to stock.

If you look closely at their claims they show slight HP increases, but only when running the engine at 5000-6000 rpm's. In other words, in race cars. No difference at all in trucks typically in the 1500-2500 rpm range.

Bigger tires hurt fuel mileage. Even in the same size tires with an aggressive mud tread will cost you about 2 mpg over an all terrain or street tire.

Now some good news. The bigger tires mean your odometer and speedometer are not accurate. You are driving farther than the odometer is showing so when you figure fuel mileage you are doing a LITTLE better than you think. Probably no more than 1 mpg, but still an improvement.

With that engine and with "normal" size tires I'd expect about 12 mpg city, 16-17 mpg hwy.

 

That mileage is low. Its around the mileage my 2008 3/4 ton w/5.4 was getting around town.

 

According to fuelly, about 14-15mpg is the "normal"

http://www.fuelly.com/car/ford/f-150...4&submodel_id=

I don't know if the 2010 has the adaptive transmission but you could try a KAM reset.

Also try cleaning the throttle body and MAF/MAP sensors (don't know which ones the 2010 has exactly) sensors.

Finally make sure to use top tier fuel (www.toptiergas.com). It will help clean the internals even morel .

 

For pure city driving, I don't know that 10.4 is that bad. Fuelly puts that truck at 14-15 which is going to show mixed driving.

But like marshallr said, there isn't anything aftermarket that you can add that will affect fuel economy enough to cover the costs. Spending $600 on an exhaust system to save maybe $50 a year doesn't make financial sense.

What you can do is normal maintenance items. Make sure your sparkplugs are fresh and gapped property. Stay up on oil changes with quality oil. Some engines are particular on fuel as well (my last truck got measurably better fuel economy on Shell gas, though it doesn't seem to matter with my current truck). Keep that air filter clean, (although K&N filters actually protect your engine better the dirtier they get).

I'd put money on your tires being the worst culprit, when its time to replace them go back to stock sized as large tires can REALLY hurt fuel economy. Put on highway tires too, or at the least a mild all-terrain; heavy mud tires with high rolling resistance will burn through the fuel. If your truck has a lift removing that will help some too, though not as much if you're always driving city speeds.

 

I'd take out the air filter and go with OEM. Aftermarket CAI, which your stock already is a CAI, increases airflow offset by less filtration. But, the stock flow is already more than the truck can use. So you aren't benefiting your truck but actually hurting it. I'm not sure by how much, but you aren't seeing any mileage or HP improvements. Sure it sounds better, but at a cost