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Poor Gas Mileage, 5.3L

Poor Gas Mileage, 5.3L

Postby cadebriggle [OP] » Jun 23 2012, 8:27pm

Hey guys, I'm hoping that some of you can help me figure out what is causing my truck to get the fuel mileage it's getting. Before I start explaining I understand that I drive a truck and I don't expect 25 mpg out of it but I do like to think that I should get better than what I am getting.

I bought my truck about a month ago. It is a 2010 Silverado Ext. Cab Z71 4x4 with 9,000 miles. The truck has a few aftermarket parts that I know of, An Airaid CAI, Gibson cutback exhaust, and it has the rough country 2 inch leveling kit. I'm also running BF Goodrich All Terrain tires 285/65R/18. Since I've had the truck I have filled it up twice. I calculated my mileage after my first tank and it came out to 12.9 mpg. I calculated my mileage again after the second tank which included about 200 miles of highway driving and it came out to 15 mpg.

Doesn't this seem low for a 5.3L? I know it has slightly larger tires and the 2 inch leveling kit but I figured the exhaust and CAI would make up for whatever mpg I'm loosing. The only thing I can think of is if the truck had been programed prior to my buying it and that is whats causing me to loose gas mileage. If this is the case where could I take it to have it checked? I don't think taking it to the local chevrolet dealership is my best option since they might void my warranty if they find out it has been programed.
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Re: Poor Gas Mileage, 5.3L

Postby Trumpster1 » Jun 23 2012, 8:33pm

Sounds about right to me. I'm lucky to get 14.5 - 15 mpg with my stock Silvy. Those tires and lift are not helping matters any.
EDIT: Also, even highway driving 55 - 65 mph I was getting 18.

Quick question: how do you like the growl of that Gibson exhaust and CAI?
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Poor Gas Mileage, 5.3L

Postby happyhourhero » Jun 23 2012, 8:36pm

Ya I'm averaging 14.6 basically all stop and go driving.
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Re: Poor Gas Mileage, 5.3L

Postby EKinMN » Jun 23 2012, 9:34pm

I get about 18.2, across all driving. I have been averaging that for the last several months. But, my truck is totally stock with regard to exhaust, suspension, etc. Leveling will probably cost you a few MPG's. Possible the CAI and exhaust do, too. If they are using more air, they have to be using more fuel.
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Re: Poor Gas Mileage, 5.3L

Postby Babies_Dadeo » Jun 23 2012, 9:48pm

I am running about 18ish highway, if I consciously keep my foot out of it, and 13 to 14 around town. Keep in mind i am running 4.10s so I spin the motor a little faster at speed. Given the lift and the offroad tires, I would think you are in the right ballpark.
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Re: Poor Gas Mileage, 5.3L

Postby cadebriggle [OP] » Jun 23 2012, 9:53pm

Thanks for all the input. I thought that the CAI and exhaust would only improve gas mileage but I guess that is something I should read up on some more. I was really hoping on this last tank being mostly highway that I would get around 17-18 mpg, but maybe I'm just out of luck. I have a 2005 camry for good gas mileage :).

Trumpster to answer your question, I love the sound of it. I do get some drone when it switches to 4 cyl. but it doesn't bother me. It sounds awesome on the low end and it's not to loud when your cruising so it's the perfect choice for me.
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Re: Poor Gas Mileage, 5.3L

Postby 11 Silverado » Jun 23 2012, 10:04pm

2011 Silverado CC, 4x4 with the 5.3, 6 speed auto and 3.43 gears. 13.5 in town, 16.5 highway, and 14.4 average over the 6K miles since new. Drive it easy, and only modifications are CAI, and dual exhaust. I got the same milage before I added the CAI and exhaust though. It just sounds better now. Hoping for better after I get some more miles on it.
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Re: Poor Gas Mileage, 5.3L

Postby sulli » Jun 23 2012, 10:15pm

The Magnuson-Moss Warranty Act of 1975. The act states that a dealer must prove that aftermarket equipment caused the need for repairs before it can deny warranty coverage. If it as me I would take it to a chevy dealer and ask them to see if there is a non stock program on your computer. However, if there is a non stock program they might make you pay for it. If you bought the truck like that from another dealer then they should honor the fact that your trying to make the problem right. To fix your gas problem you can buy a programmer. I am thinking of getting a Hypertech Max energy programmer which in most cases you will see a 1-2.5 MPG increase as long as you can learn to keep your foot off the peddle, its tempting with extra HP, but you will see a gain from all the forums ive read. The cheapest I have found is on http://www.autoanything.com and use the promo code WELCOME15 and it will be $288.99 with free shipping. Hope this helps
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Re: Poor Gas Mileage, 5.3L

Postby Voodoo » Jun 23 2012, 10:35pm

'11 Silverado, 5.3, 6 speed, 3.73 rear, K&N Cai, Flowmaster muffler back......17.5 city, 21.5 Highway. I'm running stock tires on 9" wide rims. 2" level and 3" blocks in the back.

This has been discussed to death. It's really hard for me to believe that these trucks come off the same line and vary so greatly in mileage. But they sure do. Hopefully you can find something to help 'er out a little.

Do you have a cap/tonneau cover? Seems like tonneau equipped trucks pick up a little. Capped trucks lose a little....weight maybe?
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Re: Poor Gas Mileage, 5.3L

Postby VORTEC429 » Jun 23 2012, 11:06pm

I average around 18.5-19.2 lately. Bone stock 75% country roads/highway and 25% city driving. Like Voodoo said every truck is different. My mother in law has same truck as me 2 years older same everything tho and gets 16.2 at best. Depending on the tune they put on the truck it may be hungry for premium fuel. good luck!
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