What kind of mileage from a k3500?

I recently bought a used 98 k3500 extended cab dually with a 350 vortec and the 4L80 transmission. I am getting about 11 miles to the gallon. It seems
pretty consistent whether pulling, towing, or town driving. Is 11 miles to the gallon good or should it be a little better? After driving and exiting the vehicle I always smell gas fumes but have detected no leaks.
thank Danny
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sounds about right to me. Whats yoru rear differential gear? Could be a little better with a tune up ( the works), I had a 89 3/4 4x4 ext. cab with a 350 and after a good tune up i went from 9-10 to 12.5 mpg regularly.
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wrote:

You're on the low end of OK, given it's a dually and probably has 4.10's.. We've got a '98 C6P C2500 at work w/ a 350, 4l80E and 3.73's and it gets 14-15 around town and 17 on the highway empty.
-Bret
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I have a 2000 GMC Sierra 3500 with the 350 vortec and 4L80E and getting 13 MPG around home and I am not happy with it either. Around home for me is a rural area and I think it should do better. Haven't had it on a road trip yet so don't know what to expect there.
Have to admit it runs good so I haven't even looked at the plugs or anything. Could have original ones in it for all I know. It has 112000 on it, and is also a crew cab, but wouldn't think the CC would make much difference on gas milage. Charles

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