Chevy Silverado and GMC Sierra Forum banner
Cancel
Create thread New Garage Forums

Poor Gas Mileage, 5.3L

Jump to Latest
85K views 43 replies 32 participants last post by  larryderouin  
C
#1 ·
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.
 
#4 ·
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.
 
Save
Reply Quote Like Like
C
#6 ·
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.
 
#7 ·
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.
 
Save
Reply Quote Like Like
S
#8 ·
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
 
#9 ·
'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?
 
#10 ·
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!
 
#14 ·
I have a leveling kit on my truck with some beefy all terrains, Their not oversized I think I got 275 70 R17s But I'll average 20ish driving extremely economical and about 16 to 17 driving with out being so conscious. K&N box airfilter with single in dual out flowmasters and a Diablo sport 87 tune
 
Save
Reply Quote Like Like
J
#15 ·
what most people dont mention is the differant conditions there driving in. what terain hills or flat, temp, octain fuel, speed, calculated or from what the truck is telling them, tuned or not, trany and how they drive. My 4 speed 5.3l w/373 gears in the summer with 93octain 10% ethinsh*t got 16.5 if drove no more then 55mph. in town 14, hiway 65mph it got 13 or 14. I had a performance 93 tune that got better mileage then stock. That 4cyl mode does absolutly nothing but make the truck run like crap for the secound its activated in NY.
 
#17 ·
I almost have the same set-up you (Airaid, Gibson exhaust) do but here are my differences:
2wd
stock suspension
BFGR A/Ts
Hypertech chip

I get around 14ish city and 20+ highway. I never drive over 63 on the highway and it makes a huge difference. The BFGR don't help and if I had some tamer highway tires I could prbably add another mpg or 2. Ethanol free gas will help a lot if it's available.

My advice, search for some good tuner software, ease off on the throttle, and use ethanol free gas if its available.
 
Save
Reply Quote Like Like
#18 ·
I have the 2011 11,000 miles crew cab short box 5.3 with 3.42 and I average 17.8 to 18.1 driving 60-65. It isn't any better than my 2001 5.3 that averaged about the same. I hooked up to 26' travel trailer 5,800 lbs. this past week and pulled it down from Hot Springs Ark. To SE Texas. Three tanks averaged a whopping 8.3 mpg. Ouch! Other forums all say about the same thing. The truck pulled it just fine with the 6 speed transmission doing its job very well. I just couldnt keep gas in my truck.
 
S
#19 ·
I hit about 16-17 with an unmodified 2wd so your numbers (with the mods you list) sound like they are reasonable.

What type of gas are you using (E85, 10% Ethanol, which octane, etc)?
 
Save
Reply Quote Like Like
#20 ·
After reading countless threads about this, I've come to believe it all has to do with driving style. My 2010 5.3 4x4 with 3.42 gears is on 18.3 avg (both DIC and similar #'s by hand) in the 12k miles since I bought it. This is gonna be in very similar conditions to Jeff (all around NE Ohio).

I'm not accusing anyone of anything, but I don't think there is an inherent variability in the trucks. Some people crush the throttle, others carry 300 lbs at all times, etc. Head-to-head isn't a great comparison. Plus you just ain't gonna get good #'s outta eight cylinders!
 
#21 ·
I burn regular unleaded 10%Ethinol. I was thinking about trying unleaded plus on our next trip. We have a trip tomorrow that's about 80 miles from home. I keep a light foot but going up hills it ranges from 2500 to 3500 rpm's. The truck is rated for 9,600 trailer towing compactly and I'm pulling around 6,300. I wouldn't want to I'll anything heavier. The crazy thing is that after burning 3 tanks of gas on our trip home the fuel range has adjusted itself to 250 miles after filling up when I got home. It still reads about 233 miles after driving it to work the last three nights. It should read 430 miles when I fill it up. One forum says it takes a while driving without the trailer for it to change. I hope so.
 
#24 ·
Shouldn't hurt warranty because it doesn't effect the engine. Would only affect it if you just ran open manifolds. Just keep it legal just in case you got to take it into the shop :)
 
Save
Reply Quote Like Like
#25 ·
I researched the warranty about the exhaust and air filter before I installed them on my silverado. The only way it will void your warranty is if there is damage to the engine or a system in the truck due to the modification. If you experience a problem and the certified GM Technician determins it to be legitimate and nothing to to with the modification, your warranty will remain in tact.
 
#26 ·
Hate to be the bearer of bad news but that is about right if you drive like a teenager. If you drive like grandpa then you can get a little better but not much my truck is bone stock and driving to and from work every day i average 16 to 17 max with a 50/50 mixture of stop and go and highway if i do a sustained drive on the highway 60/65 (driving like grandpa) my best average is 20/21 P.S if i do my daily drive to work not in a hurry my best average is 18.5 but in a hurry (like most of the time) i get 16/17 to and from work but with your truck with the programer and all the aftermarket stuff it is normal to use more fuel what i would recommend is get a different programmer one that you can control the mixture for example some have modes that you can change the program too like Sport mode Race mode and ECO mode and Tow mode. P.S.S Why did you do all the math? Doesn't you truck do the math for you like mine does ;) mine gives me Fuel used, average MPG, trans temp, instant ECONOMY V8/V4, and fuel range yours should do the same i assume. What MPG do you get according to the DIC? ;)
 
Chevy Silverado and GMC Sierra Forum
posts
1.5M
members
232K
Since
2009
A forum community dedicated to Chevrolet Silverado and GMC Sierra pickup owners and enthusiasts. Come join the discussion about performance, modifications, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
Vortec 5300 5.3L V8 Exterior - Body - Frame Suspension - Steering ⛐ Electrical ⚡ Uncategorized Truck Topics 🛻