What kind of mileage can I get out of a 1500 1998 4x4, can I expect 15 or better? I am looking at putting a 350 in my 1998 that has a 305 and have heard I can get a little better mileage out of the 350 and more power

 

What shape is your 305 in? If it isn't a high mileage motor and it is running fine you can squeeze some good HP out of it with some modofications.

 

I just hear those 305s are garbage

 

I have a 350 engine in excellent condition, with 3.73 gears, 80K miles and I get 12-13 in town and maybe 15 on the road,

10 mpg towing a 6K trailer.

mpg will also depend on your gears.

 

YEP,15 IS STRETCHING IT..more like 13-14

 

Yup sounds bout right. I get bout 12.5 around town but if I am divin it back and forth to work a get between15 and 16.

 

In my '93 with a 5.7l, I have tweaked 15-17 in town. My record is 24 mpg going from Klamath Falls, OR (4,300 ft.) to Gold Beach, OR (sea level) and back.

I run the engine very cool, lean, and with hotter plugs.

Seems to do great with this set up. Done some other stuff too but I think these things were key.

A lot depends on you driving habits too. I would say I am average. I pass people a lot to stay around 68 mph on the highway.

 

I have a 94 half ton 4 wheel drive 5.7 and I get between 12 and 13. And I don't step on it either, lol...

 

Well I had a 1990 with a 5.7, 373 gears with lets just say lots of miles on it and I was averaging 16 to 17 in town and 19 to 22 on the freeway. Now it was not a 4x4 and it had a few mods, but definately a well worn out motor. Build a ram air set up with a k &n and it will help it alot... other mods I had were an intake manifold, shorty headers, underdrive pulleys, Hypertech thermomaster chi[p and 160 degree thermostat, glasspack and then dualed after it.
If you need a ram air design setup, mine might work on yours too.