So I just bought an 04 1500 with the 5.3 in it. I knew that I would not get great gas mileage out of this but sure thought that it would be better than 8.82 miles per gallon city.

Did I buy this and it has a modification that I do no know of that is making the mileage so bad?

I do have after market tires on it. But they are still 265/70 r17's. No lift on it.

Basically I am just lost and am wondering if there is something I am missing?

 

I own a 2004 - also with the 5.3L and shod with 265/70R17 tires. (My truck is a 2wd, by the way.)

I get 14 in city driving and typically get 16 or 17 with mostly highway driving; but did manage to squeeze out 19 miles per gallon on a trip to Michigan last August.

My neighbor has a 2008 with a 5.3L and he gets 11 or 12 around town - probably because he has 4x4 and very low gearing.

How many miles are on your truck? Have you changed the spark plugs? How is your air filter? What type of axle ratio do you have? I know there are more questions, but those are the first ones that came to mind this evening.

Good luck finding out what is causing such lousy fuel economy. That costs big bucks these days, as gasoline is now well over three dollars a gallon nearly everywhere.

 

In my 05 Z71 I get 14+ avg in the winter running to work and back. Around 17 highway. In the summer I can get 16+ and 18-19 for the same driving.

Does your truck seem to run good?

 

130,000. I have the service records and do not see a tune up anywhere in there. Air filter looks as though it was used in a wood shop. But I am thinking of putting in a k%n or something of that sort. I cannot remember the ratio but would that make that big of a difference?

Truck seems to run in great condition.

 

The filter will make a good difference and yes the ratio could be a factor...depending on what you have. You could have 3:42 or 3:73 depending on if you have a tow package i think, not 100% sure on that one though

 

Ok so I checked and it has a 3.73 ratio.

 

I don't care which rear end you have < 9 mpg sucks. Even the 4.10 will get way better than that.

 

Yeah so I thought about changing the fuel filter. Nope, have to replace the whole pump.

 

try changing the plugs and wires, stick with ac delco plugs. and change the air filter