I've been a very bad boy a LOT of the time, and I'm getting in the low to mid 20s (auto trans).I do have more rural than city driving though. I use a calculator-don't trust the car.
Try doing that, and use the same pump if you can so the car is the same level when you fill.

 

I wonder if the 2010's are as bad as they seem on paper with the 3.73's? Seems like even 2010's with 2.55's can average 25 mpg.

Are the 3.73's really that bad on fuel?

 

Good points -- sorry about that, I forgot the car is still in break-in , please disregard my suggestions to shift at 2000 RPM! Much better to let it rev and drive it hard during break-in.

Thanks for your concern Charlie, but don't worry, my 4.6 sees 6K quite regularly . . . . hmmmm, come to think of it, it's probably about time I found out what the rev limiter feels like, and confirm the rumors about the tach flashing red at redline . . .

 

I let it get up there from time to time and, unfortunately, have been doing all city driving so far so that I'm really varying the rpms. I have already bumped the rev limiter once . With the 3.55s, I'm hitting 60 mph in second gear about a split second before the rpms hit the limiter. Oops!

I don't know that I'll be able to shift at 2000 rpm even after the break-in. I haven't owned a Mustang before the 2011 5.0, but I gather from folks on the forum that most GTs throughout history have had a lot of low-end torque that peaks early. The 2011 GT seems, to me, different from that and a lot more like European sports cars. Below 3000 rpm, the new 5.0 has okay power and pickup, but the full 412 really kicks you in the seat at 3000 and above. I don't know that I can give up that feeling by keeping it around 2000. I'm willing to sacrifice a little mpg for that feeling. 10 just seemed a bit low given the EPA estimates.

I'll give it a thousand or 1500 miles and see where she's running. Also, I'm taking a little road trip this weekend so I'll get a chance to guage highway miles.

 

I just hit 1,000 miles on the clock last weekend and my MPG is right at 16.7. Not as high as I'd hoped, but I'm hoping that it continues to go up as I drive it more. It was around 12-13 for a while with a few hundred miles on it.

 

I believe that the EPA testing is done on cars that have 5000 miles on them. It's going to take a while for the engine to reach it's maximum efficiency. In the meantime, have fun and don't worry about it.

 

i have 4300 miles on mine and the computer has me at 21.6 mpg and i have never reset it.

when i took the car on a 2400 mile trip it got up to 24.1 but actual milage and fillups put all my mpg between 25.2 and 27.1 and i have 3.73s so i dont think its to bad for 412 hp

 

My 2010 GT with 3.73 gears has averaged around 15.5-16 mpg city and 24.5 mpg highway. I could probably do better than this if I stayed out of the loud pedal more often. I've had my car a year and this has been consistent.

 

My car now has about 4K miles on it. I've habitually filled up with 91 octane at one of two 'discount' gas stations. After break-in, I have routinely seen 19 - 20 mpg on the dash display. Last weekend, I thought I would splurge and fill up with a different brand of gas for its advertised engine-cleaning properties. It was 91 octane E10. I then took a passenger for a 1-1/2 hour spirited joyride. When we got back to town, my passenger asked about my mpg, which was 19.4. Not even 5 minutes later, I looked at the dash and saw it had changed to (gasp) 13.5! It's climbed back up to around 15 over the past week, but I can't wait to run the rest of this crap out of my tank and get some real gas back in there.

 

+1... this even changes the numbers for my V6 dramatically... thats why i reset mine alot to see how im doing each day/week

 

If you want really good gas mileage you can't cruise around in 1st, 2nd, or 3rd. Those are all the fun gears but they chew through gas in those gears. Most times in the city I'm driving in 4th or 5th gear (doing 40mph) and I've got a GT500. Many times I shift right from 2nd to 4th. When you see the gas mileage numbers from Ford it's because that's how they test the cars as well.

 

412hp requires about 46lb/minute of airflow depending on BSFC/VE.

at 12.5-13:1 air fuel ratio = bad gas mileage regardless of engine displacement.


hp takes fuel.

 

The manual says that the average is based on the last 500 miles.

 

If you guys continue to rely on the mileage readout as being the accurate measure of your average fuel economy over the whole tank of gas you are going to be constantly disappointed. You have to fill it up and calculate the miles against gallons used. Most everyone who does this ends up getting better numbers than the readout shows.

 

I'm getting roughly 16 MPG with mostly city driving in heavy traffic.

What really annoys me is the tiny fuel capacity. 16 gallons for a thirsty engine like this? C'mon! Need a 20 gallon tank for greater highway range!

 

You're also calculating that based on the engine actually operating at 412bhp, which is quite a bit more than the usual 40-70hp used in city scenario's. Unless he's creeping towards 75% throttle or more, and over the 5000RPM mark between stop lights, his MPG figure is far, far from stellar.

I've been averaging about 22MPG (calculated, not from the read out) for the last 2 weeks, and that's with several strip runs vs. my father's Mustang

 

Not going to happen on the S197 most likely. The fuel tank is mounted in the center of the car above and just forward of the rear diff. It's there for safety reasons obviously but moving it would be a major redesign in the car and there's not much room there to add another four gallons of fuel. I'm lucky though, I have the 4.0 and I'm averaging 21 mpg around town and still having plenty of fun. On the highway I average 27. I agree it is a small tank for a thisty GT engine, especially the 5.0 motor.

 

That's probably one of the few things I miss from my Z. It had a 19.2 gallon tank and you could pull 28-30 mpg on a flat highway and seemingly drive forever!

And with the daily grind I only had to fill up once a week vs. twice with the Mustang.

But I guess if they can't fit a bigger tank then 16 will have to do!

 

I saw the 25 MPG & laughed thinking no way! It took me 20 miles to find out about that reset button. Went from 12.8 to it being a much better #. I'm getting 26 now going 70. I sure hope that can be fixed on yours!

 

I feel like my mileage will improve after I get used to my exhaust. I keep gunning it at every chance I get!