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Discussion Starter #1 (Edited)
my 2012 V6 is making 16.7 mpg in the city and its a v6???
my boy's v8 2014 gets 21mpg city.... i dont understand whats wrong with mine. even when it was full stock i got 18.2 city and high 19s in the HW. i tried changing the spark plugs and it didnt seem to do anything. is this normal on a v6?

Coincidentally before I went on a road trip, the day before I had timed my car to the 3.73s and drove from miami to the keys which is a low traffic straight shot drive and got around 19.7 mpgs


My mods are
Airaid CAI
3.73s
93oct Race tune i believe, race or performace i can't remember.

I will add that it is a Automatic and has currently 77k miles.
 

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How many miles? That is low. I get 20 city, 30 hwy on my 2014 v6. But then again, I have the stock gears. Change the air filter lately?
 

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On a stock 2012 v6 you should be getting about 19 city and 28 or 30 on the highway depending on your trans type but you didn't say which you have.
The 3.73s will definitely impact your mileage significantly. Stock on a 2012 v6 is either 2.72(code CC on door data plate) or 3.31(code GG).
Did you ever change your speedo gear when you did the gear swap? That'll mess with the speed being registered from how fast you are actually going thusly impacting your mpg.
 

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Discussion Starter #4
How many miles? That is low. I get 20 city, 30 hwy on my 2014 v6. But then again, I have the stock gears. Change the air filter lately?
Thanks, I bought it at 70k so no i haven't and I don't know if its ever been changed, I'll look into it and see if it works....

On a stock 2012 v6 you should be getting about 19 city and 28 or 30 on the highway depending on your trans type but you didn't say which you have.
The 3.73s will definitely impact your mileage significantly. Stock on a 2012 v6 is either 2.72(code CC on door data plate) or 3.31(code GG).
Did you ever change your speedo gear when you did the gear swap? That'll mess with the speed being registered from how fast you are actually going thusly impacting your mpg.
By change my speedo gear you mean tune the car to the new 3.73s? Then yes ofcourse.
 

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If the tune has been updated to 3.73 then either it's the low gear ratio and/or perhaps the race tune which will further lower mpg.
The air filter would be good to check however I wouldn't expect a lot of mpg to be gained even if dirty since the PCM will adjust the fuel mixture to compensate for less air.
 

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Discussion Starter #6 (Edited by Moderator)
If the tune has been updated to 3.73 then either it's the low gear ratio and/or perhaps the race tune which will further lower mpg.
The air filter would be good to check however I wouldn't expect a lot of mpg to be gained even if dirty since the PCM will adjust the fuel mixture to compensate for less air.

Thank you big guy, should I go a performance tune? I'm not planning on racing, neither is my car ready to anyways but I'm 80% certain I have on the performace tune, ive heard to also check the fuel filter as well, I know I'm in a mustang I'm not looking for civic econ but I just felt it was a bit lower than I wanted cause when i was fully stock with 273s I had poor mpg anyways, my foot isn't too heavy either, Miami cops have a keen eye for sports cars these months
 

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Yes I'd probably try a different tune, either "performance" or "street" depending on what you have. Wouldn't hurt to talk to the tuner, if you can do that.

Also calculate your mileage by hand, and reset the mileage meter, just to make sure you are looking at correct numbers.
 
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Is there a way to find out what the air to fuel ratio is? How did the spark plugs look? The tune might be running mega rich resulting in poor mpg. The 3.73’s aren’t helping the cause though since it has the motor turning more rpm than it would if you had a 3.31.
 

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Here is a snapshot from fuelly.com on 78 v6 or 3.7L, so to be fair.. you only get 28-30 mpg on flat highway speeds. It helps if there's a little wind pushing you along too.

780100
 
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