Bad MPG (what do I do?)

I know these trucks are not known for their great fuel efficiency, I thought I knew what i was getting myself into, but boy was I wrong.
I have a 2012 Tacoma 4.0 5 speed auto, the tires I currently have are 265/70R17 Ko2 from BFG, I have a bullbar with lights and the Toyota Roof Racks, along with a bed cover. I know these accesories affect your fuel efficiency but I was expecting around 13 in the city at worst. Im not a speed demon and I normally drive carefully since the street etiquette where i live isnt the best (by that i mean people run red lights a lot, dont yield and almost never stop at an intersection, so i play it safe)Best mpg ive seen in this truck in 10 months was ~13 in a trip to the beach, which was on the highway, around the city I average 9-10 mpg.
What ive determined (i live in Costa Rica) is most likely that i do have to give it more gas pretty much in every hill (Costa Rica has a lot of elevation changes). I can feel the heavy deceleration and have to keep it around 3/4 throttle every time theres an uphill so i dont lose the speed im carrying.
What should I do?
Ive read the fuel maps from Toyota are pretty rich, so maybe a tune?
What im mainly considering is a regear, since this truck might be geared for the US highways which are mostly flat.


Is there a possibility of something wrong with my truck?
I know the previous owner had a Tunit chip (similar to pedal commander) is there a possibility it has fouled spark plugs from the fuel difference? (It doesnt have a misfire)
Is there anything I should check?

 

Check for any air intake leaks and clean the MAF if you haven't already. Check the air filter.
I agree that's on the low side of the mpg's. My main travels are up and down hills and mountains. Rarely anything flat and in town I'll get 13 and hwy 17 to 18. If flat, then I get 20 mpg. I have HD sliders and 32" tires.

 

Plugs are spec'd to be replaced every 30k miles on the v6. Cleaning the throttle body and MAF sensor with their respective cleaners will help also. When cleaning the MAF, don't touch that thing off to the side that looks like a uvula. It's delicate and the part is expensive.

Welcome to TW btw...

 

While I can relate to your experience of needing more gas on hills, it's certainly not held 3/4 of the way down, and you definitely shouldn't be getting 13 MPG.

Even when I first got the truck at 62k miles, with my heavy ass WRX foot the lowest I got was 16MPG

 

3/4 of the throttle might be a bit exaggerated but I certainly have to plant it a bit more

 

haha yeah, figured as much.

I'd look into the above fixes first though. you definitely shouldn't be getting that low of MPG unless there's a bunch of armor you're not telling us about. I personally am cruising around daily with an 80lb plate bumper, 110lb roof rack, nerf boards, and a bunch of small stuff that adds up and I still average about 17 city/hwy

 

Thanks for the welcome, Ill look into changing the spark plugs