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Discussion Starter #1
Im just wondering about what kinda gas mile i should be getting. I just got this truck its a extended cab 1998 gmc z71 k1500 with the 14 bolt. and im averaging like 10 to 11 likes to the gallon. 5.8 gallons get me about 45-60 miles depend on driving style. the only thing different from stock is that it has 285 ATs on it. And i just put new fuel filter, spark plug, and wires.
 
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what gears are in the 14 bolt...when i had that same truck with 33x12.50 on 15x10's I averaged close to 14-15 in town and 16-17 on highway
 

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Discussion Starter #4
I have no idea what gears are in it. Someone told me sense it has the 14 bolt it have a a 4l80e trans. But i wish i could get 14
 

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Discussion Starter #6
Yeah but i drive easy, the rpm gauge dosnt go over 2grand.
 

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Was it reprogrammed for larger tires?
 

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flight medic
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if your speedo was not recaliberated it would throw your numbers off pretty far.
 

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yea you can't forget to correct your mileage math for the difference in tire size. Honestly you probably won't get better than 12-14 in real world conditions. My 1993 and 1995 although 2500s didn't get over 12mpgs. You may have the light duty 2500 with the 14 bolt semi float axle and 6lug wheels.
 

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FoTfive'dpokinoutdaside
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15-17
 

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Rest in Pieces
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Our 94 ext cab Z71 silverado gets 15-16mpg with the 350 and (I'm pretty sure) 3.73s.
 

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meow
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Should be able to pull 15-16 if you granny it :imo Sea Foam, plugs, tune, etc. and it will come back to life :imo
 

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Discussion Starter #16
I did put plugs wires and i ran some sea foam and still shitty
 

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my 95 usually gets between 14-high15's around town, with the 5.7 and 3.43 gears.
 
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