1996 vortec 5.7l gas mileage

[Emanuel]

I have a clogged up cat and I'm throwing a code but my combined mpg city/highway I get 13 mpg . I was wondering what to expect when I get these issues fixed . Highway I get 15 . I'm on 33s and its wrapped around 20x12s

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[DaltonB98]

I'm not sure what you planned on really getting, or if my truck just gets terrible gas mileage too. But i average 14-16 mostly highway, I assume thats about the average for most of these trucks.

 

[90halfton]

What gear ratio are you running? 33's and mpgs rarely cross paths.

 

[Jrgunn5150]

In my 3/4 ton I'm getting mid 15's so far. I also have a pretty rough running truck, so i haven't gotten a "clean" tank yet.

 

[90halfton]

Has your speedo been corrected for tire size? That will throw off your odometer as well.

 

[camaroman101]

My swap from 265s to 285s actually corrected my speedo somehow. I've got 3.23s A4 and get around 10mpg city.

 

[Jrgunn5150]

My swap from 265s to 285s actually corrected my speedo somehow. I've got 3.23s A4 and get around 10mpg city.

I'm supposed to have 245's, and it's still reading high with 265's lol.

 

[MDR-97-Z71]

My swap from 265s to 285s actually corrected my speedo somehow. I've got 3.23s A4 and get around 10mpg city.

My k1500 did the same, I have 3.42 gears and 285's and my speedo got corrected can't say it's affected my mileage considering I get about 15mpg.


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[Ironhead]

My bone stock 98 5.7 automatic seems to get around 14 in town, 18 on the highway. That's a heckuva lot better than my 69 350 4bbl auto GMC, which seems to get a combined 11 mpg. Mind you, it has a light camper on the bed.

 

[Emanuel]

3.73 the gas milage isn't that bad for an old truck and it threw it off by 1 mile not bad . I'm at 278k and this truck is running great besides the cats and the o2 code for the right cat