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Discussion Starter · #1 ·
I know we've all see the 20/28 MPG and been a little down on it. Some have question GM's ability to make engines with a VVT engine producing such a lower MPG values. Well I thought I'd bring up some data a came across recently I have seen mentioned else where on the forums yet.

Pontiac now has the official pricing ($17,990) and specs for the i4 varient of the G6 on its website.
ECOTEC 2.4L 4 Cylinder MFI engine with 167 hp

EPA mileage estimates 23/34 (city/highway mpg)
As I had speculated before it seems the tuning done to the Solstice's version of the 2.4L VVT has greatly impacted the Fuel Economy values of this engine. Being a Roadster it's higher CD and gearing also hurt this, but the G6 Sedan is also a much heavier car too. I thought people might be interested to see this engine is able to get better fuel economy depending on how it's tuned. You could possibly even get the ECU programming from the G6 applied to a special ECU for your Solstice if you wanted to drop power but get better fuel economy. :D It wouldn't be as good due to the high CD and gearing, and would require someone to go over it correctly so you don't mess your ECU up. A tri mode option would be cool. Low Power/High MPG, Base Power/Average MPG, 100 Octane High Power/Low MPG.
 

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The highway number is so much lower that it just has to be gearing, at least in part. Aerodynamics play a big role in highway mileage, of course, but I wouldn't expect either car to be much more aerodynamic than the other (although roadsters are usually not so great in that dept because of their short overall length). I bet the G6 is turning a lot lower rpm at highway speeds.
 

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Oh man! If this car had 23/34 (city/highway mpg) I would have been a 1st 1000 owner. :) It is good to know that the engine can produce good fuel economy when tuned for it.

Here's a question. Does the EPA have the top up or down when it comes up with MPG? It seems that would make a big difference.
 

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Discussion Starter · #5 ·
stang said:
Oh man! If this car had 23/34 (city/highway mpg) I would have been a 1st 1000 owner. :) It is good to know that the engine can produce good fuel economy when tuned for it.

Here's a question. Does the EPA have the top up or down when it comes up with MPG? It seems that would make a big difference.
I believe MPG is supposed to be rated for worst case scenario. Which would mean a fully loaded vehicle with the top down.
 

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Discussion Starter · #6 ·

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i had already posted some thing like this before but when i drove it the driver info center said i was getting 29 in the city.
 

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If I was worried about fuel economy, I wouldn't be buying a turbocharged Solstice. Wait until you see those fuel-economy numbers.
 

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jimbo said:
If I was worried about fuel economy, I wouldn't be buying a turbocharged Solstice. Wait until you see those fuel-economy numbers.
Turbo is nice. Keep your foot outta the gas and the mileage is good. Get on it and you've got something extra. My Jetta 1.8T gets 30 zipping me the 5 miles back and forth to work and 34-35 when cruising at interstate speeds.
 

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The thing is the methodology of testing for the EPA is really out of date. They test freeway speeds at 50 mph (IIRC), and the City cycle really isn't that realistic either. Thats why many cars made today beat these numbers. I know my Sentra isn't supposed to break 29(highway), but I regularly get 30 to 33 mpg on summer gas, but on winter gas it drops to 27 at worst (combined on both quoted figures). I pull even more when I cruise on the freeway the whole time going from vancouver to Olympia. I'm pretty sure the Solstice will atleast meet the mileage of my Spec. The turbo version will probably match it as well, if you keep your foot off the gas. I like to think of turbos as displacement on demand :)
 

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I have always gotten higher mileage than the EPA rating on every GM vehicle I have owned.
 

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Editguy said:
I have always gotten higher mileage than the EPA rating on every GM vehicle I have owned.
Same here, my Sunfire gets 33 combined (with the exception of Winter) when I'm only supposed to get 30 combined.
 

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package said:
According to the gm media site (link is below) the Solstice is expected to get 29 highway, 20 city, and 23 combined city/highway. :cool:

Oops make that 28 highway...
 

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Discussion Starter · #16 ·
I'd like to point out the Cobalt SS Sedan and G6 Sedan Fuel Economy values listed below are from automatic transmission cars with 4 gears.
 

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I'm tired of hearing people say how poor the Solstice's fuel economy is. I think it's incredble. I'm very excited.

I currently get 12/18 premium only in my Benz.
 

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WaitingForBoost said:
The highway number is so much lower that it just has to be gearing, at least in part. Aerodynamics play a big role in highway mileage, of course, but I wouldn't expect either car to be much more aerodynamic than the other (although roadsters are usually not so great in that dept because of their short overall length). I bet the G6 is turning a lot lower rpm at highway speeds.
I think gearing explains an awful lot about it. I don't know about the I4, but the G6 with 200 HP V6 has a 3.05:1 rear end and is rated at 34 MPG.

The G6 GT with the same 200 HP V6 has a 3.91:1 rear end, with a 0.68 top gear overdrive and is rated at 30 MPG.

The Solstice with 177 HP and less weight and the same 3.91:1 rear end and a lower 0.73 top gear overdrive is rated at 18 MPG.

MY CONCLUSION:

The open-topped Sosltice with a lower top gear overdrive ration of .73:1 gets 2 MPG less than the Pontiac G6 GT with the seam rear gear of 3.91:1. Between an open top and slightly lower gearing, the Solstice loses 2 MPG to the very similarly geared G6 GT. No doubt engine tuning would produce slightly better economy numbers, but put a 3.05:1 rear in the Solstice and you would probably get around 31-32 MPG highway.
 

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jimbo said:
The Solstice with 177 HP and less weight and the same 3.91:1 rear end and a lower 0.73 top gear overdrive is rated at 18 MPG.
Where are you getting the 18mpg figure?
 

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I'm currently getting 12-15 mpg (if i'm lucky, going downhill with a tailwind) in my '79 camaro, so whatever the Solstice is will definitely be better than that.
Oh well, my wife's Saturn SL1 5-speed gets about 33-34 city and anywhere from 40-45 highway.
 
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