Getting better than 13 mpg average in my 1994 GMC 4x4 - What can I do to get better fuel mileage out of my 1994 GMC 4x4 Pickup? It currently ...

What can I do to get better fuel mileage out of my 1994 GMC 4x4 Pickup? It currently has a 1995 5.7L V8 with 262,000 miles on the engine and 312,000 on the truck. The engine is still running good and getting the factory average fuel mileage of around 13 mpg. I had thought about upgrading to a 5.3L, but my research has shown that a 5.3L does not get much better on fuel mileage.

You will get better gas mileage from the 5.3L, but it doesn't make sense to drop a few grand on an engine swap just to save a few bucks at the pump. You've got an engine that has over a quarter-million miles on it, and if you treat it right, it's good for another quarter million, at least. My previous truck was a 1997 Sierra with the 5.7L, and it got about 13-14 MPG before I put a cat-back exhaust on it. After that, it was more like 14-16 MPG. It had about 300K on the clock when I traded it in.

On an engine that old, I would just focus on basic maintenance, and be happy you've still got a reliable truck. You could try the exhaust like I did, but I don't know how it will respond, since I think my 5.7L was slightly different than yours.

I have a 93 k2500 5.7 and get the same average as you do less when towing its around 8-10mpg pulling 7000# gooseneck. Just driving highway no trailer 14mpg and all time best is 17 mpg going 65 -70 . I would just keep the 5.7 however if you have a shop that will clean your tbi that really made my mpg go up.

you can not put a 5.3 in that truck without spending a shit load of money! you would have to change every electrical wire in that truck to work with the 5.3. i had a 94 and when i bought it i rebuilt the motor and found out it was from a 1998 5.7L Vortech and that truck ran like shit with that motor could not find a intake that fit the vortech heads that would take a older style TBI!!!!! had to use the old style TB because thats how the truck shifted! i would had to either pull the motor and put a non vortech or change tranny, computer, wire harness, and the $1500 for the holley throttle body that would work on that motor! i just spent 2k rebuilding the motor!!!!!!!!!! so i sold it AS IS lol

Thanks for the replies. I am going to stick with the 5.7L. I like the cat back exhaust idea and cleaning the throttle body cleaning.