Reason for poor gas milage

I had a 1995 Silverado Z-71 with 350 engine and throttle body. Got
about 13 mpg. Changed engine due to oil consumption. Still got around
13 mpg.

Now I have a 1995 Seirra 4x4 with 350 throttle body engine and still
get 13 mpg.

Some people say that 13 mpg with 4x4 is normal. Then someone told me
that the low mpg is because it is a throttle body. They said that GM
stopped using throttle bodies because they only produce half the hp of
a carbuteror and this is why I get low mpg. I should switch to a
carburetor which is a major conversion. I later was told that this is
a minor conversion and that the vica versa (carb to throttle body) is
the hard conversion.

Now, yesterday I was told that throttle bodies produce higher mpg than
a carburetor and that my problem is probably a bad O2 sensor or a
kinked wire or a plugged catalytic converter(which I due not have
anymore). I was also told that a new computer chip could help a lot or
that my current chip could be reprogrammed.

So, whats the truth?
I can't live like this much longer.
Should I be getting 13 mpg or should it be higher?
Does throttle body get better or worst mpg that a carb?
Would a conversion be practical and possible?
How do I know if the O2 sensor is bad before replacing it?
Will a new chip help? How much help?

sofasurfer.RemoveThis@charter.net wrote:
> I had a 1995 Silverado Z-71 with 350 engine and throttle body. Got
> about 13 mpg. Changed engine due to oil consumption. Still got around
> 13 mpg.
>
> Now I have a 1995 Seirra 4x4 with 350 throttle body engine and still
> get 13 mpg.
>
> Some people say that 13 mpg with 4x4 is normal. Then someone told me
> that the low mpg is because it is a throttle body. They said that GM
> stopped using throttle bodies because they only produce half the hp of
> a carbuteror and this is why I get low mpg. I should switch to a
> carburetor which is a major conversion. I later was told that this is
> a minor conversion and that the vica versa (carb to throttle body) is
> the hard conversion.
>
> Now, yesterday I was told that throttle bodies produce higher mpg than
> a carburetor and that my problem is probably a bad O2 sensor or a
> kinked wire or a plugged catalytic converter(which I due not have
> anymore). I was also told that a new computer chip could help a lot or
> that my current chip could be reprogrammed.
>
> So, whats the truth?
> I can't live like this much longer.
> Should I be getting 13 mpg or should it be higher?

13 is about correct with a 350 in a 4X4. Consider that you have the same
basic engine BUT you just added another 750 pounds in the 4X4 gear as
well as having a taller vehicle with lower gearing.

> Does throttle body get better or worst mpg that a carb?

In the real world they get better across the wide range of engine operation.

> Would a conversion be practical and possible?

Not practical unless you want to replace just about every piece on top
of the engine, the computer, wiring harness and then fail inspection for
an illegal modification of the emissions system.

> How do I know if the O2 sensor is bad before replacing it?

Put it on a real scanner and see what the voltage values coming off of
it are. Keep in mind that there are other items that cause low mileage.
When was the last time it had plugs and wires cap and rotor? Fuel
filter? Air filter? Does it have stock size tires?

> Will a new chip help? How much help?

Not likely. The 350 has NEVER been a mpg motor.

--
Steve W.
Near Cooperstown, New York