Fuel Gt 6 Spd Owners. Whats Your Highway Mpg?

Discussion in '2010 - 2014 Specific Tech' started by Don Karnage, Dec 17, 2011.

  1. Just curious what your highway mpg is like? Not to worried about the city as 85% of my driving will be interstate.
     
  2. 6Spd Manual ofcourse ;)
     
  3. I haven't done a full trip on the highway, so it's hard to calculate exactly. I have gotten 22ish though with a mix of some city/mostly highway on a tank though. I imagine you'd see 25+mpg
     
  4. What rear end gearing do you have?
     
    Juice2012 likes this.
  5. 3:55 rear in mine......I can get 26 mpg without any speed bursts and cruising 70 or so.
     
  6. 3:73 here. 22.5MPG...
     
  7. With 3.31's 26mpg should be easy. Thanks guys
     
  8. I can get 28 mpg consistently with the cruise set at 70 (after about 1000 or so break in miles). On two lane roads going 60ish, it can do a little better. Even when I find some curvy backroads and have a little fun with it, it still gets mid 20s.

    Mine has the 3:31 rear. I also know where to go for no-ethanol gas, which helps.
     
  9. I have the 3.31 gears.
     
  10. I drive from Jacksonville FL to Dothan AL about once a month and i can do it on one tank and still drive around town for a day on the same tank so its a lot better than i thought it would be.
     
  11. Manual and 3.73 = 25mpg
     
  12. Manual, 3.73's and I'm getting 25.7-mpg on the freeway at 70mph.
     
  13. I took a 2600 mile round trip from Dallas to Florida. I only averaged about 22 mpg. However, I was crusing about 80 - 85 mph most of the trip. I have a Boss and 3.73 gears.
     
  14. 3.55 gears; 23 mpg
     
  15. 6m, 373s checked it once by hand with 700 miles on the clock. 22 MPG mixed driving
     
  16. 3:31 here about 25-25.5 at 75-80, 26ish from 70-75, and mid 28 range from 50-55 on the back roads.
     
  17. 3.73s at 80mph on the trip home I averaged 23.2mpg. Car has 200 miles on it.
     
  18. Yesterday, at 60-65 MPH in the rain on the freeway, the computer showed me 28 MPG with my 3:55's.
    Tach reads 2K at 65ish.

    '12 GT, 6Man, BBK CAI, Flowmasters (American Thunder, axle backs), Brembo Package, 3:55's.
     
  19. I did a simple test of 1 hour on the freeway, 70 mph, A/C on (I think). 6-speed manny tranny with 3.73s. I could only pull 22-24 mpg. The car is turning 2,250 rpm in 6th. My 2007 with 3.55s would turn the same rpm in 5th and could squeak 30-32 mpg at 70 when driving for hours.

    What I find puzzling is that if both cars turn the same rpm at the same mph, why the huge variance in mpg?
     
  20. A lot of things affect fuel mileage. Gas today tends to have more ethanol in it than just a few years ago, so there is about 2 mpg right there.

    Did you do this test recently? Winter blend gas tends to give lower fuel economy than the summer blend. Winter temperatures significantly reduce fuel mileage as well (air resistance increases about 10% for every 50 degrees the temperature cools). Have you checked your tires, cold winter temperatures mean the pressures fall if you don't add any air. Last year, I was getting about 28-30 mpg on long trips with my 2011 GT (with 3.31s) during the summer, but later in the fall, just before I put it into storage, it was struggling to make it to 25 mpg for all of the above reasons.

    Break-in could also be an issue, if you don't have many miles on it. And, surprisingly enough, the number of miles you have on your tires can make a huge fuel mileage difference. As tires wear and age, their rolling resistance goes down significantly. Your new car has new tires, and the 2007s would have been more worn. My daily driver/commuter car used to get about 34 mpg when it was new. It gradually improved a little every summer until at 6 years and 80K miles on the original tires, it was getting around 40-41 mpg regularly. Then, I repleaced the tires, and it immediately fell back down to about 34. (You could actually feel from the driver's seat that it didn't coast as well anymore). The second set of tires is now about half worn, and the fuel economy is back up to about 37-38 again.