11.55 average mpg with my 5.3

Driving pattern is 75% urban 25% highway.  I have 56k on the odometer; the engine sounds and runs like new.  All's clean under the hood, no leaks.  It's a 2013.

When I fill her up the average mpg is no more than 11 point something.  Usually mid 11's.
Neither my wife or I drive the truck hard but rather moderately.  It has stock sized tires, and no added weight.  I run standard 87 octane fuel.

Do y'all average such low mpg's as mine, 11.55?
Or are there any recommendations of what to look for in order to possibly gain an improvement?

I appreciate any comments and replies,  Thanks!

First welcome to the website!

It helps to know what year and model AV you have and to avoid having to repeat yourself you may want to add the info in your signature area of your profile.
As far as gas mileage it also helps to know how many miles is on your AV and has all maintenance been performed such as fluid and filter changes etc.?

Gas mileage on our AVs are mainly affected by driver input and rapid acceleration and braking can drop gas mileage as well as things like tire inflation. Depending on maintenance things like clogged fuel injectors or MAF sensors or even catalytic converters can affect mileage. May want to check for a sticking brake pad as well. Then you have old plugs or wires too that can affect mileage.
There are many old threads about gas mileage and it does vary but most 5.3 motor AVs get around 13-14 mpg in town and maybe 16-18 on the highway. The few with the 8.1 motor get lower mileage of course.
We tend to just accept that an AV is a 6,000 Lb truck with the aerodynamics of a brick and realize it's not bought for the gas economy....

KenFox202 said:

Driving pattern is 75% urban 25% highway.  I have 56k on the odometer; the engine sounds and runs like new.  All's clean under the hood, no leaks.  It's a 2013.

When I fill her up the average mpg is no more than 11 point something.  Usually mid 11's.
Neither my wife or I drive the truck hard but rather moderately.  It has stock sized tires, and no added weight.  I run standard 87 octane fuel.

Do y'all average such low mpg's as mine, 11.55?
Or are there any recommendations of what to look for in order to possibly gain an improvement?

I appreciate any comments and replies,  Thanks!

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11 mpg is pretty poor, even for the city.  Take a look at this: Note that 11mpg is EPA in-city estimate for your vehicle running on E85.  They are usually pretty close.
https://www.fueleconomy.gov/feg/noframes/32478.shtml
I'm wondering if your vehicle thinks you are running on E85 and is giving it the fuel volume required to accomplish it?  Would be plenty rich, but probably would not misfire from it.  It would be hard on the cat converters, though.  Someone with a scanner should be able to tell you.  There is an alcohol content sensor that could be bad.

I appreciate the responses!

It's a 2013 5.3L Black Diamond with 56k on it.  I regularly change the oil and filter, air filter, and keep the tires inflated to 38 pounds and check them weekly.  It's never thrown up a code on the dash, for whatever that's worth....

Everything under the hood looks in very good shape, and when viewing from the underside also.  Tire wear is good.  I accelerate smoothly and coast as much as possible, braking only when necessary.  It is aggravating I can't squeeze more than 11.5mpg out of it.

Given y'all's responses, Monday morning I'm going to bring it to a fellow I trust who owns an automotive shop and have him run diagnostics on it.  I'll post the results of my endeavor.

The main culprits on something like this are plugs/wires, dirty TB, plugged air filter, bad O2 sensors or vacuum leak.

Be aware that GM has a 100,000 mile warranty (10 year?) on emissions related equipment so it is likely that whatever the issue is would be replaceable under that warranty assuming related to emissions.

This may be federally mandated to encourage lower emissions. But I am not 100% certain.

That sounds awfully low to me....with a 70/30 highway city mix, I average 17-17.5.....and that's with the AFM shut off.  That's kind of the inverse of your cycle, but even still.....

My 2003 5.3 with 139k averages about 9mpg on the street. Highway 15mpg and towing on the highway about 11mpg running 2857516. Speedometer has been recalibrated for the larger tire.

My 2004 5.3 4WD Z71 gets 15 mpg on a regular basis driving to work (1/2 on heavily traveled county roads, 1/2 city). - 19 mpg on the highway.

Your gas mileage with active fuel management and a new vehicle is horrible.  You must have a big lead foot, or huge tires, or constantly in traffic jams, or something is wrong.

Just got it out of the shop.

The MAP sensor which controls when the v8 can drop into 4cylinder mode was bad.  My computer thought the truck was always pulling a load.
Additionally had them clean the Throttle Body and MAF.

My truck is 100% stock since I bought it new off the showroom floor, and I drive it moderately, not hard.
Thanks for the info about the emissions related warranty.

I'll report back once I run a tank of gas through it!

KenFox202 said:

Just got it out of the shop.

The MAP sensor which controls when the v8 can drop into 4cylinder mode was bad. My computer thought the truck was always pulling a load.
Additionally had them clean the Throttle Body and MAF.

My truck is 100% stock since I bought it new off the showroom floor, and I drive it moderately, not hard.
Thanks for the info about the emissions related warranty.

I'll report back once I run a tank of gas through it!

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Ken,

Old post, but did the MAP sensor fix your mpg issue?

I'm dealing with a similar situation. 13' 80k miles