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Discussion Starter · #1 ·
I have my new '13 GS LS3 for 5 days now, and have driven it 107 miles. Following the break-in procedures, I've not exceeded 3,500 rpm.

All of my driving has been around town, in stop & go traffic, and occasionally cruising in 5th gear, at 45 mph, for brief periods of 5 or 6 miles.

The car is showing me 11.7 mpg. Realizing that the engine is still new, and tight, I'm guessing that I can expect about a 10 ~ 15% increase after it's broken in, is that reasoning correct?

If so, it would bring me to about 13 mph. Still pretty bad.

There are many threads devoted to discussing gas mileage, but they all place the emphasis on the best possible extended highway mileage.

I have not found any comparisons of normal every day around town driving. Don't misunderstand. I didn't buy this car expecting good gas mileage. However, I did expect to be around the 15 ~ 16 MPG mark set by GM.

I was wondering what others are experiencing with the same car, in similar around town driving?

Thanks in advance for your input.
 

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I don't have specific experiance with an LS3 however I have had an LS1 C5, an LS2 C6 with and without a cam and now an LS7 Z06 and they all got/get about the same mileage. All of them easily got over 30mpg on the highway but you aren't asking about that. Around town I normally average 15-18 mpg with strictly city and or stop and go traffic and 20-24 if I mix in some highway. Now if I have any spirited driving days that number drops to 10-12 mpg with around 7-8 mpg on the track. I have found that you never really need to go over 2k rpms to keep up with and honestly still outpace traffic. Keeping it under 2k as I putt around town keeps that mpg up pretty high but even with normal driving like you are mentioning I am definetly closer to 20mpg than farther. Again, this has been my experiance in all of my Vettes give or take 1 or 2 mpg's. Give the car some time to break in and the ECU to learn and adjust.
 

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Discussion Starter · #3 ·
... Around town I normally average 15-18 mpg with strictly city and or stop and go traffic and 20-24 if I mix in some highway. Now if I have any spirited driving days that number drops to 10-12 mpg...
My best guess tells me this is about where I'll end up. About 15, with restraint, and about 12 with my foot in the injectors on occasion.
 

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12 mpg seems really low to me when the car is not being hammered, but the amount of time stopped at traffic lights or creeping along in 2nd gear will have a big effect. I think I still get around 15 mpg in town and that is with a cam. I did notice that switching to wider tires with a softer compound killed 1 mpg as did my 3.90s.

Winter mpg is lower for me because the car idles faster and runs richer until warm. Probably not much of an issue for you. ;)
 

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Discussion Starter · #5 ·
12 mpg seems really low to me when the car is not being hammered, but the amount of time stopped at traffic lights or creeping along in 2nd gear will have a big effect. I think I still get around 15 mpg in town and that is with a cam. I did notice that switching to wider tires with a softer compound killed 1 mpg as did my 3.90s.

Winter mpg is lower for me because the car idles faster and runs richer until warm. Probably not much of an issue for you. ;)
Thanks for your input, it's appreciated, and no, warm up is no issue in South Florida, ha!
 

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On average around town I get 19-20mpg. My drive to work and back is about 1/2 on highway and the rest in DC heavy traffic. If I start to push it then that will drop into the teens. I have an 08 LS3 with manual. Going down to NC on 40 running with car on cruise control at 85 got 27mpg. When I was on the track at Pocono's last summer I was running about 11mpg or less.
 

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Who gets 30+ MPG? If you really do what have you done to your car for modifications. I get around 26-28 MPG Hwy going 70. 2008 LS3.
As I stated in my post I easily get over 30mpg in my 2010 Z06. Furthermore I got 30+ MPG in my bolt on C5 and 30+MPG in my cammed 430whp LS2 C6. It is more than possible and given the fact that I've done it with 3 different platforms and levels of tune I would say that it is closer to the rule than not.
 

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Who gets 30+ MPG? If you really do what have you done to your car for modifications. I get around 26-28 MPG Hwy going 70. 2008 LS3.
Could be you're at a higher altitude or dealing with more hills than us. I could get 30 mpg on a fairly level highway at 70 mph back when the car had headers/intake/tune. I tend to set the speed to match traffic and let cruise control do the rest.

As the car sits I'm down at 26 - 28 mpg on the highway at 70. Z51 + 3.90s = short 6th gear.
 
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