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Bad Gas Mileage Causes? 03 2wd

FultonD33

Full Member
Joined
Oct 22, 2019
Messages
39
I have the 03 2wd AVY On Road Edition so I would expect a little better gas mileage than I am getting. Last tank I got 10mpg but I got new tires and this tank I got 11.5. I have completely stock suspension except new stock height shocks and springs. I run 31.5" tires I think on stock wheels. My mileage is currently at 156k. I have a CAI and stock exhaust. Would an aftermarket exhaust setup help? Maybe just performance muffler?

The only thing I can thing of is maybe the plugs and wires need replacing. I do not know the last time they were done I got this vehicle from a one owner its always been babied but who knows if the plugs and wires were ever done. What plugs and wires do you recommend? ACDELCO?
 
There are many threads about gas mileage on this website and you can find tons of info doing a word search. The biggest effect on gas mileage is the way you drive the AV, it is a heavy vehicle with the aerodynamics of a brick and will never get great gas mileage. You should drive the AV as an old person and try to avoid rapid starts and stops. It does best at highway speeds below 70mph and trying to avoid stop and go driving.
Then if you are using the onboard computer for gas mileage it is infamous for it's inaccuracy. Best to check mpg by checking mileage at each fill up and compare to gallons used.
I don't put much faith in CAI advertising hype about mpg and most owners don't see an increase in mpg, maybe some performance gain and definitely a gain in intake noise when accelerating. Some performance gain can come from a good CAT back exhaust but in general it's liike a CAI in that any gains on mpg are negated when the driver stomps the gas pedal to hear the intake or exhaust. Then some members say you need to get an electronic tuner to get the most out of CAI and CAT back exhaust.
 
Check O2 up stream O2 sensors
IS cat getting plugged?
Tune up will help: Plugs, Wires, air filter.
Top tier fuel helps... that is EXXON, SHELL etc...
Less city driving more interstate.
Stock tires and wheels.
More lift and coast

You should be getting at least 16-17 mpg per tank if majority is highway..
Now in the city all the time yeah 10 is what ya get...
 
Just for reference, my 2003 Z-66 has an overall average MPG of 13.92 over the past 7400 miles that I have owned the truck.

I hand track all of my fuel usage in both of my trucks.

That's just something I have always done as a simple matter of interest to me.

The Z-66 is completely stock and I replaced the spark plugs, wires and filters shortly after I bought it used back in February of 2020.

I only use ACDelco parts for the plugs and wires and I use NAPA Gold air filters.

I use Mobil 1 5W-30 with NAPA Platinum oil filters changed at around 5K miles.

The throttle body and mass airflow sensor have both been removed and cleaned.

The OEM factory exhaust system and air intake hardware are still intact.

The tires are a stock size and are listed below in my signature.

My Z-66 has 249K miles on it and currently has no check engine light showing.

I use regular grade fuel, which is usually the common E-10.

I don't bother finding any non-ethanol fuel to use.

My normal travel these days is mostly city driving with maybe 10% on the freeway.

For the most part, the terrain in my area is reasonably flat with the occasional hill.

I have yet to tow more than a utility trailer and a riding lawn mower with this truck.

I also drive like the old man I am.

Meaning, if I drive down the street in front of you, we can probably wave at each other twice before I am out of sight.

:cool:
 
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