I bought a 2002 Silverado 5.3 with 114k about six months ago. Check engine light stays on due to the previous owner removing the catalytic converter. Since driving it, I've been averaging around 13mpg with combination of city/hwy driving. I've owned these trucks before and the the mpg wasn't quite this bad. The truck does have a 2in leveling kit and 33 in tires. I've done all the routine checks like tire pressure, air filter, and I don't drive with my foot to floor either. It seems like no matter how gingerly I drive, it's 13-14 mpg. Here's the my question: 1st- Does that sound typical? 2nd- Can the fact the catalytic converter is out effect the fuel mileage? Last, will a programmer help with the fuel mileage? I've been looking at either getting a professional tune or buying a Bullydog programmer. Any thoughts or comments would be appreciated.

 

the mpg sounds about right.
I get 15-16mpg combined city/hwy with my 2000 4.8L bone stock truck.


The vehicle will still operate in closed loop with the cats gone. It will not meter fuel any different. it may scavenge exhaust gases different with lower exhaust backpressure...some backpressure is desirable but I doubt you will notice a difference.


driving with the tailgate down or removed will lose you 1mpg. putting a tonneau cover on will get 1mpg improvement.


a tuner may get another 1-2mpg.


kinda funny on some level; "my jacked up 4x4 with oversized tires gets bad gas mileage"....if I had a nickel

 

Because your catalytic converter is gone your truck is now breathing better. Now that it is exhaling better it will demand more to inhale, consequently increasing your fuel millage. Because of your check engine light your ECM is possibly over compensating by adding more fuel

The Bully Dog programer maybe the answer. I think it will even clear that check engine fault.

 

that's obd I programming. A dtc for the 02 cross counts will not force open loop operation in a obdII vehicle.

 

I stand corrected, I honestly shouldn't be commenting on stuff I don't work on (only read about) and leave it to the guys that do

 

I've read your posts and seen your work; pretty talented imo.