There is no reason for you to be using 91 octane fuel. The calibration is optimized using 87. Try a few tankfuls with "the cheap stuff" and you may actually see an increase in fuel economy beyond what you are seeing now. It is a good idea to keep using the Ethanol free fuel as you will see about 1-2 MPG better than the E10 stuff.

 

I realize this, however the only E-Free fuel in my town is 91 and only at one station. May be able to get E-Free 87 somewhere in my county, but doing so would not be all that convienent to do every week. If I can find it (know of two POSSIBLE places), I'll definitely give it a try for a few weeks.

The engine has 10.5:1 compression, so it definitely has the ability to take advantage of 91 Octane with a flash tuner anyway. I'll definitely be looking into this within the next year.

Doug

 

It was my understanding that the 3.7 benefits from the same 10hp increase from running 91, as the 5.0 does. The 5.0 is rated at 402hp on 87. They rated it at 412 (on 91) to be closer to the Camaro and Chally, and rated the 3.7 at 305 (on 87) so as to not step on leftover 2010 GT's toes....a 315hp GT doesn't sound very good with a 315hp V6 sitting right next to it getting 7mpg more for about the same price.

I fully expect Ford to up the V6 power rating to 315hp next year, once most of the 2010 inventory is gone.

 

That is good! My 2010 Mustang GT (4.6L/5-speed manual/3:31 axle) would get 28mpg on long highway trips. In mixed driving, it would get 18-20mpg.

My 2011 Mustang GT (5.0L/6-speed auto/3:15 axle) has 2,000 miles on it now and is getting 19-21mpg in mixed city driving. I haven't been on any long highway trips yet to see what the new 5.0 auto will do. I will take this opportunity to also say the 2011 GT is one helluva refined car. Incredible!

 

Update ... just refueled this morning ...

computer said 28.1 AVE MPG, but 405.3 MI / 13.759 GAL = 29.46 MPG

More hwy driving on this tank than the 29.10 MPG tank last week, but not as much as a normal work week. Tuesday morning I94 into Chicago was shut down due to a Miller Lite Truck that crashed @ 3:15AM with cases of beer strewn across all 3 lanes. It was still screwed up at 7:30AM when I was on my way in, so I had to get off. Wednesday morning it was raining, so I took side streets again into work ... and because of all the rain & humidity I had the Defrost or A/C on quite a bit too.

Think it could have easily been a 30+ MPG week !!

Doug

 

Oh snap! Save the Miller Lite!!!!!!!!!!!!!!

 

Your 3.7 V6 would run door to door with a stock 428CJ and yet gets triple the mileage. Thats amazing.

While my 3.55 Geared 5.0 will never match your 2.73 geared V6 Im very happy so far. You might have something with that G100. My latest tank appears to be hovering around 24.5 mpg City (Info Center reads 22.8 mpg and is usually 7% low).

Of course since I started thinking about mileage Ive been running the AC less and turning off the car when I think Im going to be idling over 30 seconds (per manual) so Im sure that plays into it as well.

 

On paper it will walk all over my '69 too as the best I ever did in the quarter with it was 15.39 @ 93.65 MPH. It has a mildly built 351W (incl. a Crower Perfomance Cam, Offy 360 intake and 650 CFM Holley 4150 ... maybe 350 HP @ crank), wide ratio top-loader, and 3.50:1 T-Lok. It gets around 10 MPG too !!

I figure an '11 M/T V6 w/ std. 2.73 gears should be able to get in the low to mid 14's if the PP version w/ 3.31 gears did 13.7 @ 102.

I'm sure with a proper tune and the right driver my '69 could do MUCH better than 15.39, but would it really beat this '11 V6 ??

Doug

 

Thats some good gas mileage Doug. I checked my gas mileage today. Mine is all in town driving. My 4 cylinder 158 h.p. Dodge (traded for Mustang) got around 22 m.p.g. My Mustang got 23.3 m.p.g. I'm very happy with this, twice the horsepower and getting more miles per gallon than my 4 cylinder trade-in.

 

That's great mileage, my 370Z averages 22 in mixed driving, albeit spirited most of the time.

 

Thought I would post my results from a long drive this weekend. My first tank was about 18-19 MPG but that included a TON of idling and lots of spirited take offs. My second tank (in process) was the start of the 200 mile round trip. I reset the computer and off I went. By the time I was out about 30+ miles, I was at 25 MPG, all highway. Some around-town driving moved it into the 24s. More slow driving behind driver's training failures and it was moving to the 22's. Back onto the highway home and it was averaging 24+ MPG.

Not what I'd call "stellar" for the V6 but it is only the second tank AND I believe the computer is estimating low. I have the 3.31 gears as well. Heading north this weekend for a VERY LONG drive and will check again. If I can get 29 MPG, I'll be happy.

 

Jerry, you know about doing the 'cruise control' thing to reset the display for the m.p.g. Right?

 

Cruise control thing? I just hit the reset button. . .

 

No. That doesn't reset the display. With the m.p.g. dispay showing. Go on a long straight road and set your cruise control at around 45 to 50 m.p.h. Push the reset for the m.p.g. read out, you'll see your m.p.g. go way higher. After a couple miles, turn off your cruise control off.....Your done. Doing this gives you a new starting point for your read out m.p.g..............I think i told you the right way......It works for me LOL!!!

 

Interesting. I was at the gas station, not moving, and went to the MPG screen and pressed the reset button. The MPGs went to 0.0. Figured I was starting from scratch.

What possible difference could cruise control make?

 

Consistent RPMs (on a flat, straight road anyway).

 

Doesn't that defeat the purpose of average MPG? If your driving isn't always on flat, straight roads, then why would it matter when you reset it?

 

yep, I thought that was the way to do it?

Hey, that is impressive gas mileage, ALMOST makes me second guess my decision to go with the 2010 GT instead . . . actually what's more impressive is that you can get it to bark third, I haven't been able to do that (yet) in my GT . . . then again I hit 3rd at about 65 mph if I wind-out second pretty good so that might be a bit much to ask . . .

For reference on the computer, I've been tracking it over several tank-fulls, and the computer has always been within a few tenths of the calculated MPG -- sometimes a little high, sometimes a little low, but never off more than 0.5 MPG -- this probably has more to do with the accuracy of the calculation (do you fill the tank up to exactly the same spot every time?) than the computer.

 

It just gives you a better starting point. I was stuck at 17 m.p.g. before i re set it using the cruise control. Now i'm showing a more realistic 24 point something on the m.p.g. read out.

 

Indeed it does. It gives you the best possible scenario for highway mileage. It's kind of like seeing how many laps you can do around a banked race track with the cruise control on while averaging 45 MPH. A mostly pointless and unrealistic test when compared to average MPG.

It gives you a nice boosted average to start out with though...