32 replies to this topic

[alstairs]

I have a brand new LTZ 1500 Silverado with 5.3L engine. I have been really disappointed to date (2 weeks) with the fuel mileage. As a brief test, I tried turning on the 4WD High. The AFM seemed to be on more often, turning the engine into 4Cyl mode. Also, I reset the fuel mileage before doing this, and my average fuel mileage was better.

Is there anyone out there that has seen this, and is there a fix? I could be way off, but it almost seems like a programming error in the AFM. I can't understand why the fuel mileage would be better in 4WD, and the AFM was switching into 4Cyl mode at a noticeably longer period of time. (I checked it on the same stretch of road i drive every day...)

Thanks for any help, this is a great site.

Al

[ed c]

What do you consider to be "disappointing fuel mileage"?

[doodeediddledodindee]

Unless you want to see if they will cover your drivetrain under warranty I wouldn't drive around in 4hi on dry roads unless you are only going straight

[markw8]

You need 5000+ miles before worrying about gas mileage. Also if your looking at the DIC for current mileage, you should watch it over a couple of tanks.

Mark

[06SierraZ71]

You need 5000+ miles before worrying about gas mileage. Also if your looking at the DIC for current mileage, you should watch it over a couple of tanks.

Mark

+1
When my truck was new, it wasn't until I hit 10k miles before my mileage stopped going up.

[govtech4]

omg

[alstairs]

Thanks everyone.Yes, I only had it on going straight. It looks like 16MPG in 2WD, 18MPG in 4WD. Maybe I'm being too eager to resolve this, and based on above I should give it a little time. I wasn't sure if I was fooling myself in hoping it would get better. Sounds like it may.

[Mattersnot2me]

Was this actual mileage or computer display mileage? The onboard display on my truck isn't terribly incorrect, but never matches the actual "fill-refill" mileage. I wish that my 2011 "Z" would get 16 mpg on the highway! It currently has 4,000 miles and is getting better, but even though I live in very flat terrain the best I've seen was 15.5 mpg, and while towing my 2000 lb. boat, around 12.75 mpg. This was using very easy starts and going no more than 55 mph.

[waumo1]

My 2011 5.3L Ext Cab LB 4WD only has 2600 miles but it is reading 15.5 MPG over that distance. We don't have any flat terrain in my state....

[rdnkcpa]

The best mileage I have ever gotten with my 5.3 4X4 with a 3.73 rear end has been 19MPG. That was one time, driving it strictly hwy and really trying to squeeze every MPG I could. I usually come right in between 16.5 & 17. That has been over the life of the truck, which is 8 years and 129,000 miles.

My FIL has a 2009 2WD Silverado with the 5.3 AFM, he gets right around 20MPG highway.

I wonder if on the Honda Civic forums they ask how they can get more payload in their Civics.

[joshrt24]

the truck says mine gets average of 16.5, I drive mostly highway not interstate so there is a lot of slowing down and speeding back up when people turn etc... I would be interested to see how mine does on an interstate trip. btw its a 2wd 1500 5.3

[z71silverado12]

I am new to this forum and found it through a search engine. I am having extremely low gas mileage and wanted to see what you all thought.

I have a 2012 Silverado 5.3L with 850 miles on it. I have gone through 3 tanks of gas and found that I am getting 11.7 MPG. I dropped it off at the dealership yesterday and the lead technician told me that the MPG that I was getting is "average" and it is in fact correct. He said that all of the trucks that come in are getting between 11.5-12.5 and that is what they are supposed to be getting. I basically told him that he was nuts since the window sticker states (as well as fueleconomy.gov) that City 15 MPG and Highway 21 MPG and everyone that I talk to with the same truck is getting 15.8 MPG. I also said that a friend of mine which has a 2010 (without the fuel saving 8cyl to 4cyl shifting thing) and he is getting better MPG than mine. The tech told me that he doesn't believe me....

What do you think about the 11.7 MPG?

Just FYI, I tried to return the truck the second day that I owned it because the transmission or engine is acting funny (shifting hard, downshifting even harder, etc..). I have also had some electrical issues; the remote starter didn't work but would recognize that I was pressing the start button but nothing happened (I have it on video), the door sensor was acting up showing that the driver door was ajar when it was closed (I also have these 2 separate instances on video). I called GM and told them everything as well and they stated that I would have to take it to the dealership.

Oh yeah, 8 days after I bought it GM started the "love it or return it" special!!

[crankman]

You need to finish a good break in of your engine before getting wound up about mileage. markw8 IS RIGHT ON about needing at least 5000 plus miles to loosen her up a bit.

[z71silverado12]

You need to finish a good break in of your engine before getting wound up about mileage. markw8 IS RIGHT ON about needing at least 5000 plus miles to loosen her up a bit.

Do you think that it will change by that much and go up to 15.xx MPG?

[crankman]

Very possibly if you dont have a lead foot. There a bit optimistic about the MPG on the stickers for real world but with a 5.3 it can happen.