Extreme Mileage Issues?
 

Alright I know nobody buys trucks for mileage, but I went from my average of around 14 miles per gallon city down to around 8 miles per gallon city, and I have not changed anything on the truck. Just redid the oil with a K&N oil filter, full synthetic (5w20, i think, had a mechanic do it). Truck has 71,419 miles on it
2008 Ranger XLT
4.0L SOHC V6
5 Speed Automatic Transmission
4x4
4.10 Rear Gearing

K&N Drop in Air Filter - Flowmaster Exhaust (Muffler) - Magnaflow Twin High Flow Cats - Diablosport Tuner (i used to get 14 MPG with all of these parts)

Does the engine need a tune up? Plugs, wires, coil?
I run injector cleaner and seafoam through it twice a month

Thanks All

Never mind guys I'm trading the ranger in for an older one with a four banger

I get anywhere from 17-21 mpg with a 01 2x4 extended cab with a 3.73 gear

I have basically the same truck as yours: a 2008 FX4 model with a little over 72k on it, and still get about 20 mpg when I keep it below 65.

City driving just kills mileage in general. How is it on the highway?

also if you've been using the air conditioning, it kills the mileage as well. thank god my truck isn't my dd lol

AND… letting it idle while you run in the store or just to cool it down, there goes another mile per gal.

On a good day I think I am around 12 with 3.0/33s/4.10s/std/ and a heavy foot.