92 having problems

I have a 92 4wd 3.0 ext cab with 57000 mil. First is the gas mileage problem. I get anywhere from 12-13 mpg. Now i'm not sure how quick these things take off or what there top speed is but i get about 90 mph top end and about 13s for 0-60. I think that may be average. I had a leaky fuel enjector that was replaced. other than that, i haven't replaced anything. i bought the truck with 52000 mil. any suggestions?

Lots of things affect fuel economy.
Tire size
Brakes
Tire pressure
Air intake (is it clean?)
air/fuel mixture
engine oil weight
driving habits/driving conditions
The first thing I would look at is the spark plugs to see if you are running rich.

is it an auto if so 12-13 mpg is about right

i agree with kimMG if the first see if it is running rich, that narrows the possibilites allot.

however even with an automatic in it, you should get much better than 12 er 13 mine gets between 20 and 22