gas mileage

[93killerbee]

I need some help, i just installed a magnaflow 2 1/2 inch cat-back system with 3 inch tips, before the install i would get about 300 miles out of a full tank of gas now im getting about 200 miles out of a full tank? my mods are upper/lower typhoon intake mac 1 5/8 equals 2 1/2 inch h-pipe, cold air intake. im running 93 octane gas. any help would be good.

 

[Bone Racing]

a/f ratio?
maybe your open exhaust made the car breath heavier and its become very inefficent

 

[ECU5.0]

hmm....is it just because you like the power and are stomping on it all the time? could be a number of things....cant think of anything off the top of my head thouhg

 

[MadMatt5oh]

I have the same problem, I have a lose connection on the dist. Old plugs and wires, etc. Cant fill the tank or it pisses out the gas. Ive only been able to drive it one weekend but 100 miles to a tank is absolutely unacceptable!

 

[blkstangman88]

Thats not to bad cuz my 88 gt only or still gets 230 thru 280 to the tank, depending on how heavy my foot feels.

 

[ALMOSTFINISHED]

gas

u people are real lucky. i can only manage about 140 out of a full tank of 93. thats city driving. it sucks but what can u do when u have a mustang right?

 

[blkstangman88]

i think there somthing wrong with ur car......everyt think of a ignition set up? i got a complete msd ignition set up and i got a couple extra mpg.

 

[blkstangman88]

i think there somthing wrong with ur car......ever think of a ignition set up? i got a complete msd ignition set up and i got a couple extra mpg.

 

[remat457]

My motor is stock but didn't lose gas mileage when I put the same catback and a 2.5" H pipe on...must be something else...

 

[65ShelbyClone]

All the mods in my sig still get me 21mpg, which is about 260-280 useable miles before having to fill up. Thats only marginally worse than with a stock engine.

A cat back alone shouldnt cut your mileage down by 1/3. Like everyone else said, it could be a number of things. First make sure your right foot didnt get more agressive.

 

[blk92stangg]

65Shelby, do your drive highway miles or city? Since Honolulu is one big traffic jam all day, I am getting about 180-200 a tank...I would LOVE to get the mileage you do.

 

[TenorPlayinGuy]

my car averages about 210 to 230 mpg ... but i have a 4cly tranny so im not reading actual mileage... im actually getting my 300 per tank... but i cant tell... my car only has headers, straight h, and flows and still gets good mileage... im going to a flex fan, and underdrive pullies with a k&n to get some more mileage though.
but like everyone said... a change like that tends to make your right foot more stompy and man can it make a difference on gas milieage... and in so cal this time of year bad mileage is a BAD thing... gas jumped to 2.45 for 93 here... im gonna need a second job JUST TO PAY for gas to get to my other job... lol

doh well cant live without the stang...

 

[87'GTstang]

21 mpg on a 267k miles original 5.0.

If your car is designed to run 87 octane, just run 87 octane. 93 shows no benefit except being down on power because your car's timing cannot take advantage of it. What kind of shape are your oxygen sensors in?

 

[Pod]

Hehe, you think gas/petrol is expensive there. You should try England.
79p per litre.
£2.98 per US gallon (3.78 litres per gallon)
$5.07 per US gallon (1.7 dollars per pound, roughly)

5 bucks!
and you think 2.45 is a lot!

As for mpg, I'm not really sure about mine, as the fuel gauge doesn't work. I get about 200 miles before the fuel light comes on which is when I fill it up. Completely stock except for an offroad h-pipe and no silencer. Mixture of city and highway and a bit of fun every now and again.

 

[blkstangman88]

running 87 gas in a 5.0 HO is the dumbest thing ive ever heard, every time i even thought of putting that crap in my 5.0, my car started pinging and backfiring. i dont care what ppl say, i only put 93 in my stang. with 93 gas i get way better response time, and mpg and with the 87, all it does is clog fuel injectors and filters.

 

[1Slow5oh]

Wow you people should feel blessed...... my car gets around 160 per gallon...... and that was before the 4.10's im screwed now..... any suggestions on how to reduce this??? i might have junk o2 sensors would that be doing it????

 

[ninety15.0]

i think i had the same kinda problem when i did my full exhaust....but it went away really quick when i realized it was only cuz i wanted to hear that signature sound. Keep your foot out of the pedal and u will do a lot better....the other things is do a big tune up... i went from getting 20 mpg on the highway to ust over 27 just by doing a full tune up. good luck man

 

[Highway High]

What does a full tune up consist of? Im getting around 12 mpg every fill up Granted, I don't keep my foot out of it, but I really dont drive it too aggressively now, just the occassional romp. I drive a lot and freaking filling up like every other day is starting to get expensive.

Logan

 

[87'GTstang]

running 87 gas in a 5.0 HO is the dumbest thing ive ever heard, every time i even thought of putting that crap in my 5.0, my car started pinging and backfiring. i dont care what ppl say, i only put 93 in my stang. with 93 gas i get way better response time, and mpg and with the 87, all it does is clog fuel injectors and filters.

Put it this way, your car came off of the assembly line designed to run 87, and at one point it ran perfectly - plain and simple. That my friend is called hiding a problem and trying to cover it up - until it catches back up with your engine. The only way it would run better with 93 and worse with 87 is if your ECU was reprogrammed and its MAP curves altered either digitally by a computer, ECU controller, or a computer chip. But if not, your car is running the way it does on 87 because of a problem/malfunction.

 

[ALMOSTFINISHED]

I dont think anything is wrong with my car.. my friend has a 92 gt and gets just about the same mileage. i live in ny, maybe the gas is different or something. i have done a full tune up, fuel injector cleansing, and new o2's. i am also a master tech so i would know if something was wrong with my car.. any other suggestions please let me know.....thanks