I have posted many times on this forum about how bad of Gas mileage I have been getting in my 2007 Mustang GT/CS Convertable Automatic. I have owned it for 5 weeks now and I have taken it to the dealership 3 times for multiple issues, but mostly for MPG each time. I have calculated my MPG by dividing the miles driven by the Gallons I put into my tank when filling up. I have not gotten higher than 13.5MPG ever. I have not gotten higher than 210miles on a tank. The last time I took my car into the dealership I zero'ed out the Miles on the Odometer and had a half of tank in the car. I picked up the car and it had 43miles on it and a quarter of a tank of gas....but they hooked it up to the "Computer" and averaged 21mpg, the math says more around 13mpg. I have taken it in again this time with the Service manager, and he said he got the same results when driving it 55mph on the interstate when hooked upto the"computer". I called Ford corp. three times now an they reiterated what the dealership said to me and Ford Corp. said that the dealership has final say. I am now waiting to hear back from the dealership's customer relations manager to find out if the will do a "buy back" on my car. All I want is for them to either fix my car or exchange my car for one that actually gets the correct MPG.
Any suggestions on how to fix this problem or get some results???
Please HELP!!

 

First, do you have the on board information system? I have been using mine since I bought the car. I reset it each time I refuel. I am averaging 23.4 mpg, according to the on board computer, and I believe it, based on my driving. After purchasing the car, I drove it 1200 miles with 62 miles on the engine, and averaged 22-23 mpg, on secondary roads, as I avoided the interstates to just enjoy the ride, and see the little towns by passed by the Interstates.

Also, are you using "pure gas" or gas blended with ethanol? The blend may result in your getting reduced mileage. I experienced that with my last car while in Minneapolis using blended gas.

And, last but not least, are you driving the way the dealer folks are driving it Or, do you have a little heavier foot? Or is your driving route very much different from the one they use to test it? Ask them to drive the same route/distance you do, say going to and from work, and then evaluate the mileage.

Just some thoughts. Best of luck.

 

What kind of mods do you have? Manual or auto? What's your driving style? 3.55 rear-end if manual? mostly city or highway? short or long trips? All of these things can make a difference. I don't think you can assume that the MPG rating is a guaranteed from the manufacturer.

I average around 15 mpg, but I drive my car like I stole it, have an agressive tune, and I do mostly short city trips. I'm not surprised and I don't complain. If I was concerned about milage I wouldn't drive a V8 muscle car, but that's just me :-)

 

No on-board....I am actually doing the math with Gallons filled and miles driven.
No-gas fuel mixture....Florida doesnt believe in that ethanol stuff evidentally....no gas stations down here have that!
No heavy foot....Driving mostly in the 1250-1750Rpm range at all times...mostly coasting in traffic, and no heavy acceleration.
I know all the little rules like Tire pressure, Waxing the car, etc. But I am just plainly getting very poor fuel mileage no matter what octane I use. I drove 55miles strickly Interstate going 55-70mph to the beach and back and used over a quarter of a tank of gas.
I need options of how to get this resolved because I think the dealerships are only hooking upto the computer and then getting 20-21MPG somehow and the just quitting on looking anymore. When I call Ford Corp. they file a complaint and tell me that the dealership will contact me within a week.

 

I don't have any Mods because I have had these problems since the first week and did not want to change it so the dealership could find something I did to blame it on. It is an Automatic. Mixed driving....but calculated with driving strickly highway as previously stated and got poor results. I do not drive it like I stole it because there are around 20-30 cops I see on my trip from either home to work. I love the V8 for when I need the power, but I would like at least reasonable reults..... come on 13MPG.... I could see that if I was driving crazy, but I don't.

 

You have had the car for 5 weeks, how many miles are on it? Every new Ford I have owned never got what I considered normal mileage until it had at least 3-4000 miles on the clock. Even though there is no "break in" like the days of old, you still need time for parts to settle in. Give the girl some time to settle in before you go and pitch her...

As far as your "computer" comment-yes the service personnel would have driven the car with diagnostic equipment installed (WDS, PDS or IDS -Ford's corporate diagnostic equipment) and this does allow for pretty accurate milege tracking. I have little doubt at a steady speed of 55 that it would avg. 21 MPG. You do drive 55 in Florida all of the time, right?

Lastly-pitch the EPA rating...estimates are done entirely in computer, though this is changing for the '08 model year.

 

I would fill the car full. Have a small can of gas in the trunk and drive her until you run out of gas. I think you may be using the gas gauge as your reference point. These are not exact. You do not have a the IUP. So how are you calculating your mpg? Reading the gauge and half full and dividing by the miles traveled is not accurate...

Just my opinion...Run it out of gas and then divide miles by gallons...That is the only way you will know. Just make sure you are on a side road when you are close to being empty. You will be surprised how far you can drive when you are on empty...Good luck...

 

I live in Virginia Beach, VA and commute to and from Naval Station Norfolk (about 38 miles round trip) in both stop and go and highway conditions. I run 87 octane 10% ethenol blend in my 05 GT. The only mods on this car that could affect MPG are the removal of the snorkal filter, change over to a K&N panel filter, and Flowmaster exhaust. I regulary see 16.9 - 17.9 MPG in my commute. I'm religious about keeping the tires to the proper inflation level. I've got 21K on the odometer, mileage was lousy for the first 1000 or so miles (around 14.5-16.5 MPG); It got better as time went by. It's a V8 so I'm realistic about expected mileage. The best mileage I've obtained was the 23MPG observed on several road trips to NY and back via US Route 13/1/95.

I hope this gives you some frame of reference.

Regards,
Kevin

 

Don't EVER run your car out of gas! You'll burn up your fuel pump! All you need to do is fill to a consistent point each time you fill up. Then calculate mileage based on miles driven between fill-ups and fuel consumed. It's not rocket science. There will be some variation from fill-up to fill-up, but over the course of a few tanks you'll have a pretty good average.

BTW - This has all been discussed previously in the numerous threads already posted about this car. We're out of ideas...

 

Did you start running 87 octane?

 

Keep on them Tampa. Something is not right guy...

My auto 06 GT gets 23 mpg @ +80mph. Better when doing 65 or so. 310-340 range with full tank... and I drive aggressive whenever I can get away with it! Your ride gets a THIRD less? Geesh...gotta be somethings not right somewhere...

Good luck brother...fight the good fight!

 

wow why drive a hybrid when you can drive Mach's Mustang GT

Dead stock 3:55's fairly agressive driving no highway now averaging 16mpg on 89. I rarely use 5th under 65mph.

 

My wife's consistently gets 15.5 - 16 MPG in city driving although I fill it with 93 octane.

 

I have only had the car for 5 weeks....but the car was the manager of the dealerships Demo car for a couple months....it has 6,000miles. So that out rules the car not being broke in yet.

 

I dont have to run it out of gas.... I just drive it till the light comes on...I know it is a 16gal tank....when I fill it up I check how many miles I am putting in it...i.e 15.4 gallons and dividing that into the miles driven i.e 204miles last tank. = 13.24MPG

 

Does anyone know where the diagnostic computer reads the amount of fuel used from? There could be an issue with the fuel line before that point. That would make the computer think youre using X gallons of fuel on the motor, but wouldn't know about the Y gallons that aren't being accounted for. Have you run it on a dyno? Maybe the computer is running extra rich.

 

I am now running 87oct after many people told me to stop running 93oct. I was getting the same gas mileage with the 93oct as I was with the 87oct. The reason I switched back to the lower was because running the higher gave me a drone in the exhaust around 30-40mph that has now since gone away with 87oct.

 

Does anyone know any alternate routes to take? Ford corp says that only the dealership can make any decisions and everytime I call Ford Corp. they just redirect me to the dealership....any way to go above them?

 

Looking back at the checklist I posted here, maybe these areas are worth investigating during future diagnostic activities -

1) restriction in the air intake system
2) ignition system troubles (bad coils, etc.)
3) fuel delivery system pressures
4) exhaust system restrictions (plugged cats, etc.)
5) automatic transmission not shifting properly (staying in lower gears longer)

 

Yes, running out of gas would be a bad thing. When the light comes on is a good idea. I did not know if you had the light since you have no IUP...Was tired when I though of that...I am up now...

Best of luck. Something is definately not wrong...Keep us updated..