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Discussion Starter · #1 ·
First, I apologize this is a repost from the other 5.0 forum, didn't see this specific 94-95 one.

I have a 95 GT with around 140,000 miles.

Below are the only mods:

3.90 gears
Bama chip
Underdrive pulleys
Straight-pipe exhaust with LM1s
CAI


After I installed the gears (Late August) my highway MPG obviously went down a bit, but my town MPG wasn't changed much.

Lately my gas mileage has gotten pretty terrible, my last tank I got 120 miles on. My tank holds about 10 gallons when the gauge is just off empty.

The 120 miles was a mix of highway and in town mileage, and apart from a few short runs against my buddy's 98 GT I drove it very easy, usually shifting at 2k or 2.5k and not going over 65 on the highway.

Everything appears normal, nothing sounds different, no leaks, etc, what could be my problem? Would changing plugs and wires restore anything? (I haven't changed them, and not sure if they have been previously)

Thanks guys, I'm new to 5.0s and this is my first Mustang, so I have much to learn.

Tyler
 

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12 MPG is pretty bad I don't think I ever got worse than 16 with mine. If it just suddenly dropped like that think about how you were driving it. It will suck that fuel quick if you're dipping into the throttle a lot, plus winter temperatures and winter gas might make it drop a little bit. Last time I checked these cars had a 14 gallon tank, just thought you might like to know.
 

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Discussion Starter · #3 ·
I've read that it should have a 15 gallon tank, but I've ran it right to the bottom of the indicator and it's right at 10. I guess it could have 5 gallons extra below that, but I don't care to run it empty.

I am used to getting around 200 miles in town and I've gotten 300 on a tank on the highway driving easy. Other than the few runs against my buddy, I drive really gentle on it, I'm 100% sure it isn't a driving change. It has been very cold here lately, and I didn't know that could cause such a fuel economy change, so that may be the issue.
 

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Would changing plugs and wires restore anything? (I haven't changed them, and not sure if they have been previously)
It's worth a try changing the plugs/wires anyway as preventive maintenance even if they don't restore gas mileage.
If you've only been doing short drives in very cold weather, gas mileage may go down 'cause the engine's spending a longer time in rich warm-up open loop mode. Otherwise I'd suspect the O2 sensors as the most likely culprits.
 

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Are you sure you're not leaking gas around the donut gasket where the filler tube goes into the gas tank?

Mine started leaking at around 150,000 miles.
 

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Discussion Starter · #6 ·
I don't notice any leaks. Since the specific tank of gas where I only got 120 miles, it seems to be doing much better. Last tank got 220 with a quarter left. Hopefully it was just a freak thing.
 
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