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Old 10-10-2017, 05:50 PM   #1
thatyellowmach1
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Why is my Mach1 getting such horrible gas mileage??

Hi I am new to this forum and I need help figuring out why my mach1 is getting such bad gas mileage. Over the summer I noticed I was filling up my tank more often. Before the problem started I was averaging around 220 miles a tank, now im getting 120 miles. My driving habits are good I do not get on the gas all that often and I do pretty much all city driving. I have done I think almost everything to fix this problem. I have replaced the o2 sensors, cleaned air filter, cleaned MAF, cleaned throttle body and intake, ran fuel system cleaner, and inflated the tires properly. Did all this and nothing has changed, took my car to the ford dealership and they told me the car was having a misfire which was the first thing I check when my gas mileage was dropping but did find anything wrong. Ford fixed the misfire and I could tell right away that the car was running a lot better then before so I thought that was it, problem solved. So I filled up again and now my tank is about empty and the trip is at 125 miles, so nothing changed I am still getting the same bad mileage as before. I am a college student and I just cant afford filling up so often, so if anyone has any idea on what could be causing my gas mileage to be so bad would be greatly appreciated.
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Old 10-10-2017, 08:49 PM   #2
falcongtho3
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Re: Why is my Mach1 getting such horrible gas mileage??

Have you done a recent oil change, and if so have you checked the oil level and what kind of oil did you use?
In my 125k miles I've put on my car, this has happened once. I used Mobil 1 and it was a disaster.

borg:
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Old 10-10-2017, 10:44 PM   #3
DSG2003Mach1
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Re: Why is my Mach1 getting such horrible gas mileage??

does it struggle to start or idle? A blown FRPS (fuel rail pressure sensor) will dump fuel, so much itll contaminate the engine oil but they also usually run pretty rough from my understanding.

how do your spark plugs look? You can have a misfire without it being bad enuogh to trip the CEL but Ford can see it in their tests. Depending on mileage it might be a good idea to just go ahead and put new plugs and coils in it.

I suppose a stuck injector or one thats dumping too much fuel would be a possibility as well but again that usually comes along with a bad idle and other issues.

Does your oil dipstick smell like fuel and as mentioned above is the level higher than fuel (a sign fuel is washing down the cylinders and getting into the oil pan)
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Old 10-16-2017, 04:59 PM   #4
blown03Mach1
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Re: Why is my Mach1 getting such horrible gas mileage??

Your not running E85 are you?
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Old 10-16-2017, 06:27 PM   #5
TKat13
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Re: Why is my Mach1 getting such horrible gas mileage??

You get more than 100 miles out of tank? Wow, I should be the one pissed. Looks like a keeper to me.

Seriously, the guys above have some good advice, 'smell the oil' and report back.

Fluids and plugs tell most of the story. Good luck
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(100 shot,E85,4:10s,Street tire):60 ft - 1.67 | 1/8 - 7.88
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Old 10-17-2017, 03:57 PM   #6
Mike03Mach
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Re: Why is my Mach1 getting such horrible gas mileage??

Have you changed the fuel filter? When was it last changed?
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Old 10-17-2017, 10:59 PM   #7
DSG2003Mach1
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Re: Why is my Mach1 getting such horrible gas mileage??

Quote:
Originally Posted by Mike03Mach View Post
Have you changed the fuel filter? When was it last changed?
I donít see how this is applicable in this scenario
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Old 10-18-2017, 12:26 PM   #8
thatyellowmach1
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Re: Why is my Mach1 getting such horrible gas mileage??

Quote:
Originally Posted by falcongtho3 View Post
Have you done a recent oil change, and if so have you checked the oil level and what kind of oil did you use?
In my 125k miles I've put on my car, this has happened once. I used Mobil 1 and it was a disaster.

borg:
I am going to do an oil change soon, last time I did it I used quaker state. Is that good oil to use? what brand do you guys recommend I use? Thanks!
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Old 10-18-2017, 12:30 PM   #9
TKat13
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Re: Why is my Mach1 getting such horrible gas mileage??

I have always used Amsoil but I am currently trying out Precision's oil in my Mach, but all my other cars get Amsoil.
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Black '04 Mach 1
Track Times (bone-stock w/drs):60 ft - 1.90 | 1/8 - 8.67
(100 shot,E85,4:10s,Street tire):60 ft - 1.67 | 1/8 - 7.88
New build - 750rwhp; not track tested (yet)
Mods: Build Log
Paint&Body - WickedCustoms in Lewisville, Tx
Tuned by Manny @ HPP
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Old 10-18-2017, 12:31 PM   #10
thatyellowmach1
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Re: Why is my Mach1 getting such horrible gas mileage??

Quote:
Originally Posted by DSG2003Mach1 View Post
does it struggle to start or idle? A blown FRPS (fuel rail pressure sensor) will dump fuel, so much itll contaminate the engine oil but they also usually run pretty rough from my understanding.

how do your spark plugs look? You can have a misfire without it being bad enuogh to trip the CEL but Ford can see it in their tests. Depending on mileage it might be a good idea to just go ahead and put new plugs and coils in it.

I suppose a stuck injector or one thats dumping too much fuel would be a possibility as well but again that usually comes along with a bad idle and other issues.

Does your oil dipstick smell like fuel and as mentioned above is the level higher than fuel (a sign fuel is washing down the cylinders and getting into the oil pan)
The car runs smooth, sometimes it will idle a little low. Over the summer I cleaned and regapped the spark plugs. My car has 75,000 miles on it, should they be replaced? And I will check the dip stick and get back to you if it smells like gas or not. Thanks for the help!
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Old 10-18-2017, 02:07 PM   #11
thatyellowmach1
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Re: Why is my Mach1 getting such horrible gas mileage??

Quote:
Originally Posted by blown03Mach1 View Post
Your not running E85 are you?
no I am not
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Old 10-19-2017, 08:01 AM   #12
falcongtho3
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Re: Why is my Mach1 getting such horrible gas mileage??

Quote:
Originally Posted by thatyellowmach1 View Post
I am going to do an oil change soon, last time I did it I used quaker state. Is that good oil to use? what brand do you guys recommend I use? Thanks!
I have used Castrol Edge for about 8 or 9 years, 5w20. It is so much quieter than the motocraft blend that the dealerships use in these cars.

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Old 10-19-2017, 02:51 PM   #13
TKat13
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Re: Why is my Mach1 getting such horrible gas mileage??

Quote:
Originally Posted by thatyellowmach1 View Post
The car runs smooth, sometimes it will idle a little low. Over the summer I cleaned and regapped the spark plugs. My car has 75,000 miles on it, should they be replaced? And I will check the dip stick and get back to you if it smells like gas or not. Thanks for the help!
I never clean and gap... always gap and replace with new. (gap mine because I require a tighter gap over stock with my setup) But if your car is mostly stock, then just replace with new. I like NGKs. Less than 3.00 each.
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Darrell
Black '04 Mach 1
Track Times (bone-stock w/drs):60 ft - 1.90 | 1/8 - 8.67
(100 shot,E85,4:10s,Street tire):60 ft - 1.67 | 1/8 - 7.88
New build - 750rwhp; not track tested (yet)
Mods: Build Log
Paint&Body - WickedCustoms in Lewisville, Tx
Tuned by Manny @ HPP
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