BigDish

Hi all,

I picked up a 2005 GT convertible with a manual in it about a month ago. According to the dealer, it was a repo and it had about 1200 miles on it. The dealer drove it around and brought the mileage up to about 2,000. I've since gotten it up to about 3,100.

I'm seeing absolutely pitiful gas mileage - I filled up today and reset my MPG counter and before that reset it was about 18.6 - and that was high. Almost all my driving is highway. Oh yeah, I've also been told I drive like a grandmother - most of the time I shift at ~3000RPM.

The car's stock (to the best of my knowledge). That said, as it's a repo, I can't totally know the history. I've been running 87 octane in it. So just for fun today, I fill up my car with 93 octane (about 6 gallons went in, so it maybe works out to 90 octane), curious if it would make a difference. The ride home I got just under 23MPG. The only time I saw mileage that high was on the tank of gas from the dealer (and I have no clue what he put in) when I drove it home.

Any guesses? Is it possible my car has some sort of tune on it and that's why I'm seeing such bad mileage? Any way to tell? I know a Mustang GT isn't exactly a fuel efficient car, but I expected better than 17mpg given that I don't even come close to pushing the car to its limits.

PLstang

If your concerned about the possibilityof a tune take it to the dealer and have them reset to stock. I would think they would do it for free.

owero01

I would try a full tank of93 octane. It sounds like your tune may be set for it.

s2k

I would try to find out quick! Its not safe to be running under the tuned octane rating. I would say fill it with 93 until you find out.

Lees07GT

Can you hear it pinging (detonation) with 87?

MexGT

lol my car since new has never been over 12.5 mpg even with granny driving mod.

BillyBobJoe

from the factory, my granny driving was getting around 15.5mpg. Then I started to get used to the hydraulic clutch and drove a little more "normal" and started avgeraging maybe 16-16.5. Now with an intake, tune, and UDPs I'm getting about 18.5mpg.

WhiteStallion06

I get 22 if im lucky but thats driving not in granny mode all the time but nothing outrageous and a lot of around town stuff

Orion_240

The OP didn't make any sense!
Are you saying that 17 mpg is BAD?!
It's normal for a GT if you do a little more than half your miles in the city, with stop and go driving. 23 mpg is what you can expect on the freeway, with no flooring it.
Be sure to see if you have a 93 octane tune. If not, don't bother putting in 93 gas, as you'll be wasting $.

BigDish

I haven't heard any knocking that I can tell (except when I put it in a gear it doesn't like...this is my first manual and I'm still getting used to it)

Unfortunately, I can't take it back to the dealer I bought it from to re-flash it, as I drove about 6 hours to pick up the car :-)
I'm kind of hesitant to ask another dealer to re-flash it for fear of them trying to void my warranty.

How did my post not make sense? I specicially said almost all my driving was highway (I basically work and live right next to highway exits). The whole point of my post is I was looking for some opinions if I had a 93 octane tune - as I said, it is a repo and I have no clue (and no way to find out) if one was put on it - to the best of my knowledge there wasn't one put on it, but I'm starting to think there is. Again, I'm not flooring it, or anything even close to it.