Hob

I'll be purchasing an 05-07 Mustang GT with 50k - 70k miles most likely. After this amount of miles what MPG can I expect with an 80% highway / 20% city commute. It will likely be completely STOCK and driving it reasonably soft.

Thanks!

CMcNam

I drive like I stole it, mostly highway miles, and average 20 MPG according to the computer. I hope you didn't buy it for mileage though...

Hob

I currently own a lifted Wrangler that gets 12 - 13 hwy . Anything I get will be a huge step up for me in gas mileage so it doesn't concern me. I'm here just to see what I should be expecting.

moosestang

20+ is what I was going to say. I still get 17mpg even with all my mods.

TRexGAWD

Mostly highway? I was getting around 24-25 mpg on the interstate in my 2010.. Lowest I would average was about 18 driving in traffic through town.. I don't gun it though..

JFitz

Straight highway (I cruised at 85+ to and from Austin) you're looking at 22-25mpg or so. If you hit the sweet spot and stick (60-65) you should be around 27.

My average per tank - mix of city/highway about 30/70 - I got 20mpg. Said my car. Roughly 300 miles a tank if I remember right.

This was bone stock on engine mods.

Hob

Wow that sounds like great numbers. Very respectable.

JFitz

I wasn't apalled by it. I was moving from a Camry to a GT so I did see a drop, but I remembered why I didn't mind everytime my neighbor gave me a pissed look whenever I drove by. Guess I was disrupting his piano tuning time.

Nuke

I have an '07 GT and used to run Kentucky-to-Chicago every 2 weeks for almost a year and the rest of the time was spent pleasure cruising (not my DD). All highway on the Chicago runs, pump-to-pump, hand calculated at a pretty steady 70MPH (plus the occasional sprint up to 125 or so) with 3.55 gears I averaged 24 MPG. With the pleasure driving of mostly highway with some light to moderate non-highway traffic it was about 20-22 MPG. But a steady 90 MPH (running with a rabbit in the middle of nowwhere until the tank was nearly dead-empty) I hand calculated 17+ MPG.

I actually had 2 or more occassions where I was 55 MPH pump-to-pump and I calculated 27-28 MPG. Keep the RPM's below 1800 and she really is economical for a V8.

Suicide Bobb

So far, I've managed 14.5mpg@24mph (average speed) verified by the average mpg trip meter as well as the "gas tank fill-up" method (fill up tank, reset miles driven trip meter, fill up again, divide gallons to full tank by the trip mileage). Obviously, this was mostly city miles. When not romping on it, I pick the lowest gear possible (not 5th gear at 20mph, just whatever is above, say, 1200rpm). However, it's my third week since purchasing it, and I am still goosing it frequently.

On the highway, you can expect 30mpg at 55mph, dropping about 2.5mpg per 5mph from there on (27.5mpg@60mph, 25mpg@65mph, 22.5mpg@70mph, etc.). The speeds I listed are the accurate speeds, not the number that your speedometer points at (my speedometer reads about 4mph fast). These mpg figures were verified by the average mpg trip meter, of which I have already verified is accurate within +-0.3% (yes, a fraction of one percent). At least, it's that accurate within a 180mile trip. The less miles driven, the less accurate it will be.

My testing method to verify the accuracy of the speedometer and average speed trip meter:
1. Go on a flat highway
2. Activate cruise control as close to a solid number on the speedometer as possible (I did 60mph)
3. Reset average mph trip meter
3. Prepare stopwatch to count from 0
4. Reset miles driven trip meter and press "start" on the stopwatch at the same time
5. Press "stop" on the stopwatch at a certain mileage of your choice as soon as it passes it on the trip meter (I chose one mile since it records every tenth of a mile)
6. Divide the seconds recorded by the miles driven, and multiply by 3600

Comparing the average mph trip meter and the manual calculation, I found them to be less than 1mph different, which is more than accurate enough for what I use the average mph trip meter for. The recorded speed was about 56mph, or about 4mph less than what the speedometer represented.

My testing method to verify the accuracy of the average mpg and gallons used trip meters:
1. Go to gas station and fill up tank
2. Reset miles driven and average mpg trip meters
3. Start car, drive until as low on gas as you are comfortable (30 miles to empty, via the miles to empty trip meter, was as far as I went)
4. Repeat step 1
5. Observe the amount of gallons that it took fill up the tank
6. Divide the recorded gallons to full tank by the miles driven

My calculation was 14.55mpg (at 24mph average), and the average mpg trip meter said 14.5mpg (if it calculated within two decimal places, it may have been more accurate than what I observed). Also worth noting is that the gallons used trip meter was accurate to the tenth decimal place as well (I only recall that the gallons to full tank I observed at the pump was the same as the gallons used trip meter to its level of significance).