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Discussion Starter · #1 ·
My mpg has been a rough 30-34 ever since I got it. Ever since the last oil change, I've only gotten 16-22. What gives? Anyone experience a drastic drop in mpg?
 

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One heck of a drop

I would say the brand gas you use probably went from summer blend to winter blend along with the cold weather your car probably runs richer then in the summer. The computer does this. It will adjust for a richer mixture when the temperture goes down. Even here in Florida the gas company's have their summer blend and winter blend. My car went from 25/27MPG down to 22/25MPG since the winter blend. I'm sure you and I and not only Mustang owners notice this. Also, this is not a new thing, the gas companies have been doing this for years.

Check it out >http://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/summer-fuel1.htm

Ronnie
 

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My mpg has been a rough 30-34 ever since I got it. Ever since the last oil change, I've only gotten 16-22. What gives? Anyone experience a drastic drop in mpg?
Reset the mpg while on the freeway on cruise control at 60-65mph depending on ur speed limit and then drive 8-12miles. That should fix it and don't drive it hard for acouple more miles in the city after this aswell

---------- Post added at 09:11 AM ---------- Previous post was at 09:07 AM ----------

Reset the mpg while on the freeway on cruise control at 60-65mph depending on ur speed limit and then drive 8-12miles. That should fix it and don't drive it hard for acouple more miles in the city after this aswell
My car started telling me I was getting 13mpg once and I was like wtf!!
 

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ouch
 

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I would say the brand gas you use probably went from summer blend to winter blend along with the cold weather your car probably runs richer then in the summer. The computer does this. It will adjust for a richer mixture when the temperture goes down. Even here in Florida the gas company's have their summer blend and winter blend. My car went from 25/27MPG down to 22/25MPG since the winter blend. I'm sure you and I and not only Mustang owners notice this. Also, this is not a new thing, the gas companies have been doing this for years.

Check it out >http://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/summer-fuel1.htm

Ronnie
You sir just solved my problems! Thank you!
 

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when my car was new it seemed the dash computer was accurate to the gas I was putting in. for the last several fills the dash has read way more fule used than I am putting in. not sure why but it's obvious that the car is understating the MPG.
 

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Whitelightning said:
My mpg has been a rough 30-34 ever since I got it. Ever since the last oil change, I've only gotten 16-22. What gives? Anyone experience a drastic drop in mpg?
How accurate is your car to the actual mpg? Do you use any other instruments?
 

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The computer read is inaccurate...do it the old fashion way.
 

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the dash usualy reads 13 L/100km and my actual is closer to 11.5. thats just using my KM driven with how many L of fuel it takes to fill. it's been consistant over 5 fills.
 

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Mine has always been off, saying I use more than I do. However, I'm getting 2mpg less due to winter blend and engine warm ups. I've noticed this with EVERY vehicle I've owned. It's completely normal.
 

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Discussion Starter · #11 ·
when my car was new it seemed the dash computer was accurate to the gas I was putting in. for the last several fills the dash has read way more fule used than I am putting in. not sure why but it's obvious that the car is understating the MPG.
My car does this too.

---------- Post added at 08:38 PM ---------- Previous post was at 08:34 PM ----------

I may also add that I use only shell 87 octane. I use what is said on the oil cap 5w-20 also. My computer is reset every two tanks and it currently reads 16 mpg city driving lately. And our highway is limited to 45 mph(speed trap). Another thing is that my last check engine light was a fuel sensor. Ever since it tripped its all went to hell. Also when I drop to 35 miles or so to E and full up, it trips the check engine light every time.

---------- Post added at 08:42 PM ---------- Previous post was at 08:38 PM ----------

How accurate is your car to the actual mpg? Do you use any other instruments?
By accurate you mean old school way? Idk how to do it that way. I usually have been looking at my miles till empty and how many miles I drive and that's how I can tell its off. Then again that theory is off too since the miles till E changes by 5-15. But when it says 16-22 ill go through a tank in 3 days. 30-34 ill go maybe 2 weeks if running all the way down to E
 

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Whitelightning said:
My car does this too.

---------- Post added at 08:38 PM ---------- Previous post was at 08:34 PM ----------

I may also add that I use only shell 87 octane. I use what is said on the oil cap 5w-20 also. My computer is reset every two tanks and it currently reads 16 mpg city driving lately. And our highway is limited to 45 mph(speed trap). Another thing is that my last check engine light was a fuel sensor. Ever since it tripped its all went to hell. Also when I drop to 35 miles or so to E and full up, it trips the check engine light every time.

---------- Post added at 08:42 PM ---------- Previous post was at 08:38 PM ----------



By accurate you mean old school way? Idk how to do it that way. I usually have been looking at my miles till empty and how many miles I drive and that's how I can tell its off. Then again that theory is off too since the miles till E changes by 5-15. But when it says 16-22 ill go through a tank in 3 days. 30-34 ill go maybe 2 weeks if running all the way down to E
Lol, its simple!

Miles per gallon!

Miles divided by gallons.

I drove 478.2739miles.
I refilled with 15.345 gallons.
Miles per gallon
478.2739 / 15.345 = 31.168061 miles per gallon.

Ah, and my scanguage said 30.6 mpg, while the car said 29.6. So both were off, as usual, and the sg was closer.
 

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I reset my MPG every time I refuel. This gives the best accurate readings.
 

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Only one way to get best average MPG

First ==Fill your tank setting odometer to zero

Second== drive at least 300 or more miles

Third== Fill the tank leaving the odometer alone

forth== drive another 200 or 300 miles

Fill the tank and write down your exact milage.

Add the gallons for both fill ups together.

Then devide the total miles you went BY the combined gallons of gas you used.

Now you have the true Miles per gallon your car gets.

This is the tried and true method that people have been using for a million or so years. Check this MPG against your dash readout and I'm sure they will be different.

Ronnie
 

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I reset the average mpg in the computer every time I fill up. I also track my mileage manually using an iPhone app.

The computer has been dead on every tank since I started doing it this way.
 

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First ==Fill your tank setting odometer to zero

Second== drive at least 300 or more miles

Third== Fill the tank leaving the odometer alone

forth== drive another 200 or 300 miles

Fill the tank and write down your exact milage.

Add the gallons for both fill ups together.

Then devide the total miles you went BY the combined gallons of gas you used.

Now you have the true Miles per gallon your car gets.

This is the tried and true method that people have been using for a million or so years. Check this MPG against your dash readout and I'm sure they will be different.

Ronnie
Lol "millions of years" :p
 

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ronnie948 said:
First ==Fill your tank setting odometer to zero

Second== drive at least 300 or more miles

Third== Fill the tank leaving the odometer alone

forth== drive another 200 or 300 miles

Fill the tank and write down your exact milage.

Add the gallons for both fill ups together.

Then devide the total miles you went BY the combined gallons of gas you used.

Now you have the true Miles per gallon your car gets.

This is the tried and true method that people have been using for a million or so years. Check this MPG against your dash readout and I'm sure they will be different.

Ronnie
Yepp lol

I don't add two and then divide, but I keep track of every tank. So if one tank of 400 miles is 20 mpg, and the next tank of 400 miles is 40 mpg, it balances out and makes sense. Drastic example, but that is the purpose of it. On ecomodder, people get real particular and always use the same pump,so on. I just always use autofill on the pump, and get the cheapest fuel.
 

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Discussion Starter · #19 ·
Yepp lol

I don't add two and then divide, but I keep track of every tank. So if one tank of 400 miles is 20 mpg, and the next tank of 400 miles is 40 mpg, it balances out and makes sense. Drastic example, but that is the purpose of it. On ecomodder, people get real particular and always use the same pump,so on. I just always use autofill on the pump, and get the cheapest fuel.
I use the same station and gas. I auto fill then if possible round to the nearest quarter.
 

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I use the same station and gas. I auto fill then if possible round to the nearest quarter.
When I used a SCANGUAGE-II in my F150 (plugged into the OBD-II connector), they too recommended you use the same station, the same pump, and fuel the same time of day (temperature) to get the best, accurate readings. Not sure though how much difference it would make.

I'm happy with what the built in device provides. Resetting it every tank full works
 
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