Grand Sport MPG
11-09-2010, 07:36 AM
#1
Melting Slicks
Thread Starter
Grand Sport MPG
I am new to the LS3 engine with my recent 2011 GS purchase. The LS2 car I had ran 1500 RPM at 70 MPH and averaged around 29 MPG. My LS3 runs 1600 under the same condition and I haven't seen any higher than 25 MPG. I know the engine isn't broken in yet but I am curious as to what the rest of you are getting for gas mileage in your GS's. Is 25 MPG about what I can expect at highway speeds?
11-09-2010, 08:31 AM
#3
Melting Slicks
I have seen 27mpg on the highway - it was a short trip. I can tell you better after my Thursday trip coming up.
11-09-2010, 09:01 AM
#4
Le Mans Master
I have 3k now and most is hwy... 25 is the best you will see Have to remember there is additional weight over the coupe. If your car is an auto all of them have the 2.73 rear end as well.
11-09-2010, 09:35 AM
#5
Race Director
Plus it is widerrrrrrrr, both tires and body. I see better that the 25 mpg with my LS3 08 Base and it has a 4:10 differential with 275/305 tires!
27.5 on a 200 mile leg. I was looking to see best mileage, but still have a little fun. Avg. speed on Dic. was almost 69 mph.
27.5 on a 200 mile leg. I was looking to see best mileage, but still have a little fun. Avg. speed on Dic. was almost 69 mph.
11-09-2010, 11:15 AM
#10
Burning Brakes
On my 2010 GS (A6) I've been getting in the neighborhood of 25 mpg on the highway. If I do a lot of town driving at low speed it will drop to around 21 mpg -- either number is totally acceptable to me. I was recently on the interstate in Arkanasas and took the attached shot with my phone. I had just driven down Hwys 7/16/21 from Harrison to Clarksville (WOW!) and was then heading West on I-40 back home to Oklahoma. The cruise was set on 80 mph and the engine was turning what I call a *lazy* 1,800 RPMs. The average fuel economy for that tank (I filled up in Harrison) was 24.1. I don't think that's bad at all considering how much fun I was having! 
11-09-2010, 11:33 AM
#12
Mine is not completly broken in but i got 24.5 on a trip and had 638 miles on the car when I left with average speed of 70-75 mph. Return trip I took a curvy two lane home so that part of the trip I didn't watch mpg. The last 200 miles I rest the dic and took interstate at 60-65 and the dic showed 26.5.
My 07 got in the 32-33 highway range.
My 07 got in the 32-33 highway range.
11-09-2010, 11:50 AM
#14
Team Owner
I don't know the reason why so many GS owners are reporting that they are only getting around 25 MPG on the highway. But, I don't believe it is because of the "wide" body panels and wide tires. My 09 Z06 has the same "wide" body panels and the same wide tires as the GS. I also have 51 cu ins more engine displacement and 69 more horsepower.
It could be that the lower torque, at the low RPM's in overdrive, of the LS3, is not capable of handling the increased drag(.32 Cd vs .287 Cd of the narrow body) that the wider body panels and the wide tires have.
To offset that some, my final drive gear ratio in 6th gear is 1.71:1. The auto trans GS ratio is 1.83:1 and the manual trans GS is 1.95:1. Of course the auto trans GS has more driveline loss then the manual trans GS, so the better final gear ratio in the auto GS would be lost to the lower gear ratio of of manual trans GS. Depending on whether a base C6 has the std suspension or the Z51, the gear ratios are different. A base C6 has the same gearing as the Z06 which gives a 1.71:1 final ratio compared to the GS's 1.95:1. The more aggressive gearing that the GS probably has more influence on the gas mileage then the "wide" body panels and 'wide" tires. Thus, at any given speed, the GS is turning more RPM's the a base manual C6, which lowers gas mileage.
Running 70-75 MPH, with the cruise control engaged, down the Interstate, my Z06 gets 30MPG, with the "wide" body and the "wide" tires plus the extra displacement and horsepower. Most Z06 owners report similar gas mileage results.
It could be that the lower torque, at the low RPM's in overdrive, of the LS3, is not capable of handling the increased drag(.32 Cd vs .287 Cd of the narrow body) that the wider body panels and the wide tires have.
To offset that some, my final drive gear ratio in 6th gear is 1.71:1. The auto trans GS ratio is 1.83:1 and the manual trans GS is 1.95:1. Of course the auto trans GS has more driveline loss then the manual trans GS, so the better final gear ratio in the auto GS would be lost to the lower gear ratio of of manual trans GS. Depending on whether a base C6 has the std suspension or the Z51, the gear ratios are different. A base C6 has the same gearing as the Z06 which gives a 1.71:1 final ratio compared to the GS's 1.95:1. The more aggressive gearing that the GS probably has more influence on the gas mileage then the "wide" body panels and 'wide" tires. Thus, at any given speed, the GS is turning more RPM's the a base manual C6, which lowers gas mileage.
Running 70-75 MPH, with the cruise control engaged, down the Interstate, my Z06 gets 30MPG, with the "wide" body and the "wide" tires plus the extra displacement and horsepower. Most Z06 owners report similar gas mileage results.
Last edited by JoesC5; 11-09-2010 at 01:00 PM.
11-09-2010, 12:21 PM
#16
Team Owner
The equivalent car but in GS trim gets 25% worse gas mileage then you. Hard to believe it's from the "wide" body panels and "wide" tires. If they got 10% worse mileage, then that would put them in line with my Z06's 30 MPG. And I would still have the larger engine with more horsepower.
Let's compare the EPA ratings.
2011 coupe/vert w/LS3/A6 is 15-25 MPG, both base and GS trim.
2011 coupe/vert w/LS3/M6 is 16-26 MPG, both base and GS trim
2011 Z06 coupe w/LS7/M6 is 15-24 MPG
2011 ZR1 coupe w/LS3/M6 is 14-20 MPG.
At least, according to the guidelines that the EPA uses, they don't recognize any difference between the base and the GS trim cars, only which transmission it has.
They only see a 7.7% drop in highway gas mileage between the Z06 and the base/GS Corvette.
Last edited by JoesC5; 11-09-2010 at 01:06 PM.
11-09-2010, 01:38 PM
#18
Melting Slicks
Sleek, light, +good MPG... and in '08: $5 less than $40K!!*
*excluding sales tax & lic.
Last edited by HarleyB; 11-09-2010 at 01:41 PM.
11-09-2010, 03:45 PM
#20
Burning Brakes
I have a 2011 GS vert mn6. I get 24.5 highway and I have 3000 miles on mine.
Something just does not add up.
Base vert with same engine (no dry sump) gets 30 to 32 mpg (depending on who is quoting). Lets assume 30 for discussion.
Z06 with wide body and tires and brakes and a larger engine gets 30 mpg. And the 200 lb person setting in the passenger seat to make the weight the same does not make any difference in fuel economy so weight of car is not the issue.
I just have a hard time believing an increase in 100 to 200 rpms at 70 mph is going to reduce my fuel economy by over 5 mpg. That is just too much of a drop. I would think a Z06 or a base car running in 5th gear is going to get better than 24.5.
Again, something is not adding up. Someone from GM want to give us the real reason?
Anyone tried running higher air pressures in the tires? I am going to try 35 psi on my trip to Gatlinburg this weekend.
Something just does not add up.
Base vert with same engine (no dry sump) gets 30 to 32 mpg (depending on who is quoting). Lets assume 30 for discussion.
Z06 with wide body and tires and brakes and a larger engine gets 30 mpg. And the 200 lb person setting in the passenger seat to make the weight the same does not make any difference in fuel economy so weight of car is not the issue.
I just have a hard time believing an increase in 100 to 200 rpms at 70 mph is going to reduce my fuel economy by over 5 mpg. That is just too much of a drop. I would think a Z06 or a base car running in 5th gear is going to get better than 24.5.
Again, something is not adding up. Someone from GM want to give us the real reason?
Anyone tried running higher air pressures in the tires? I am going to try 35 psi on my trip to Gatlinburg this weekend.