Fuel filter is always good to change when you get a used vehicle, but that won't cause your symptoms.
MPG is not that great with pickups and the 4.0l SOHC engine didn't "sip" fuel so double whammy.
Gauge readings don't help with MPG, reason being is some drop fairly fast above 1/2 tank and slowly drop below 1/2 tank, has to do with the OHMs sender in the tank and gauge.
Assuming speedometer is correct, no oversized tires, so odometer is correct, then set trip odometer to 0 at next fill up and get actual MPG from what it takes to refill next time.
Gallons used for miles driven.
2010 4.0l, 4WD with automatic was rated at 15mpg combined
With manual trans it was 17 combined
Around town only driving would be 14/15mpg, so we are not talking economic vehicle.
Have them(Ford) test the fuel pressure, fuel pressure should hold for a few months when engine sits, if it is leaking pressure when it sits then it will be harder to start.
Try turning key on and off 3 times before trying to start engine, this turns on fuel pump 3 times to rebuild any lost pressure.
If this helps then you are probably looking at a pressure leak, and if you don't smell gas then it would be the check valve in the fuel pump.
This wouldn't effect driving, just starting, because after engine starts fuel pump is on all the time.
When you pull out the spark plugs look at the tips, dark brown or blackish means engine is running Rich, so lower MPG, this could be an O2 sensor issue, false lean.
If spark plugs look good, light brown or white, then O2s are good and engine isn't burning more fuel than needed.
Last edited by RonD; 02-11-2016 at 01:39 PM.