Why is my mileage so low?

[MLC Stang]

GRGT1994,

I agree with most, its your 4.10 gears!

I don't see how anybody with a 5.0 and 4.10 gears can get "20 something" MPGs without coasting downhill the entire way, or emptying the whole tank on the highway in top gear with trailing wind!

I know I'll get flamed for this, but 4.10 gears are just not the best choice for a daily driven street car. They're for shaving a few tenths off of your quarter mile time at the strip.

 

[Mustangless]

I am in the same position. Last time I filled up it was 11.3mpg. I dont have any mods and have stock 3.27s.

 

[chirs]

I live in Valdosta right now while I am going to college. I live though in Woodbine, GA. It is in the bottom right corner of GA.

By your speedo being off, you said it was off 1%. Does that mean when you traveled 10 miles, the speedo showed you actually traveled 9.9 - 9.8 miles. If that is the case, then a change in driving habits is needed. If your speedo was reading anywhere from 8.0-9.0 miles per 10 thats 10-20%. Although not much 14 * 20 is 2.8 so you would be getting 16.8 or so miles per gallon. Do you drive in the city alot? If so that is another problem.

Driving habits can also hurt you. Do you cruise on the highway with windows up at around 70? Do you use cruise control? It is actually more efficient to have windows up while using a/c than it is to have windows down. Also, using the vent fan, non a/c, with windows up can net a bigger increase than using a/c. Measuring gas mileage is also tricky. To accurately measure gas mileage, you must fill up the tank to the same point each time. I for instance, fill up my tank until the pump clicks for the first time, using same tank. Once it clicks, i hang it up. THen i drive say 100 miles. I go back to the pump and fill it up until the first click. Then i take the mileage and divide it by gallons used. I have found this to be the most accurate measurement.

 

[sKyZ]

With my car I don't really know how many MPG I get... I never bothered to look because I know it's low anyway.. Guys, we drive mustangs.. not hondas.. if gas prices and milage in a 5.0L v8 is pissing you off.. convert to being a ricer...

 

[chirs]

I am in the same position. Last time I filled up it was 11.3mpg. I dont have any mods and have stock 3.27s.

Have you done a tune-up lately. There is no way you should get that bad gas mileage unless you drive in the city at all times. Try changing O2, plugs, cap and rotor and plug wires. Also, how does your air filter look? Try chaning that as well if it looks bad. Tire inflation is also key. How many of you have front end alignments? If it has been awhile, get one of those as well. It helps keep your tires from prematurely wearing and helps with gas mileage.

Imagine if your tires look like this.

/ \

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As you could imagine, much harder to push car when wheels are toed-in.

 

[chirs]

With my car I don't really know how many MPG I get... I never bothered to look because I know it's low anyway.. Guys, we drive mustangs.. not hondas.. if gas prices and milage in a 5.0L v8 is pissing you off.. convert to being a ricer...

Not to flame, but i get roughly 26 miles highway driving. I have Gt40 induction with stock gears. My car has been tuned and has new plugs and wires. I dont see what is wrong with caring about gas mileage. If your car is not getting good gas mileage, it is not running correctly. Unless of course, modifications prevent such things. I would care though if tomorrow my car got 10 miles to the gallon. The car obviously isnt running properly and it is something that every driver should watch. I figure, every dollar saved is a dollar towards my future blower!!!!

 

[loudpedal99]

Change your fuel filter too, I changed the one in my truck and it made a 2-3 mpg difference; plus it ran a hell of a lot better.

 

[strokedandblown]

its better than getting around 6 mpg

 

[GRGT1994]

Thanks for the comments. I am running a rebuilt top end (HCI). So of course I have a tune up, new air filter. And I know that the 4.10's clearly don't help.

I'm still curious whether others with "better" fuel economy are running corrected speedo's. For example, if you are running 4.10's without any correction to your speedo, then your odo is reading 30% higher than actual mileage. Which would explain how someone could get 26 mpg.

 

[chirs]

I have stock gears. My taller tires are what is throwing off my speedo. My odo is reading 30% less than what i actually traveled. If you odo is reading 30% higher, than you get worse gas mileage. If you travel 10 miles, but your odo is reading 30% higher, than your odo would display 13 miles. This is incorrect, and would therefore lead to higher mpg than acutally achieved. Whereas, if you speedo reads low, you travel 13 but it only shows 10, you would get a lower mpg even though you traveled a longer distance. So you would see a lower mpg when infact it was higher because your odo is not counting enough miles!

 

[chirs]

That is why i was wondering if indeed your speedo was only off 1-2%. What mileage did it display after your ten mile test?

 

[Zero Signal]

Well it's like 130 miles to my friend's house in Phoenix from here. Before disconnecting my EGR, I could make it there and back on one tank with a couple miles of in town driving.

But now I'd be lucky to get 190 miles from the tank.

 

[chirs]

Do you drive with windows up and cruise control? What speed do you drive? What mods do you have done? That is WAY to low!

 

[GRGT1994]

My speedo is only off by about 1% (not 10%, 1%), which is actually better than a stock car on stock tires with their full tread.

My car is a 'vert, so I always drive with the top down (windows too, it's effeminant to put the windows up with the top down!!!). And sometimes I crank up the air conditioning if it's really hot out. Gotta support those Arabs somehow!!!

Anyway, mods are in the sig.

I still wonder about OTHERS when they claim 26 mpg on a tank. That was about what these cars were rated for factory stock, with grandma EPA in the driver's seat and not gas hogging gears or larger injectors. So it just does not seem right that anyone could AVERAGE what these cars were rated to max out at under best case conditions. But maybe that's just me.

Would anyone measuring 25 or more mpg PLEASE PLEASE PLEASE post your mods, and how close your speedo is (or how you are correcting it - speedo gear/speed cal).

 

[TheDamned]

I just filled up. And I am getting less than 14 miles per gallon now (like 13.5). WTF? See my sig for mods.

I have the timing dialed in as suggested by Trickflow and Anderson Ford. It runs like a beast now. But still I get this horrible mileage. And I read these posts from others with HCI setups saying they get close to 20 mpg (maybe they guys never corrected their speedos for aftermarket gears???).

Anyone else getting really bad mileage? Any ideas what might be my issue, or what I should look for?

dude im stock and i get 13 miles per gallon so dont complain