maxshuty

Well I put on the CAI+Tune a couple weeks ago and I drive A LOT. I ran the race tune for a tank or two of gas then my summer school started yesterday so I threw in 87 octane for my 87 "street" tune. I drove easier on the car than I did with the car stock (slower mph, less throttle, etc.) and I still came out in the hole, but just barely (around 15 miles-20 miles less than what I would get stock).
Shouldn't the CAI+Tune be giving me better MPG?? The weather is warmer which should also contribute to higher mpg, and nothing else has changed on the vehicle (tire pressure is good, fuel filter, etc etc)

Twstones

Do you mean you got 15-20 fewer miles per tank of gas? If so, that's not a very accurate was to measure gas mileage. It's better to fill your tank up as full as possible, and then keep track of the miles. Then refill and see how many gallons you used, compared to miles driven. This is somewhat more accurate, but to get a really good calculation, keep track of this for several tanks of gas. Add all the miles driven, and all the gas used. I would even try to fill up at the same station and pump if possible. The auto cut off on the gas pumps can really variety from pump to pump. Same station and pump would give you a more equal fill each time. Keep me posted of the results. I'm interested in also getting a CAI set up, but I'm also more interested in improving my gas mileage, rather that horse power. Good luck....

2005Redfire6

There is alot of factors that can cause you to lose 15-20 miles a tank. Sometimes you could be feathering the throttle or you maybe hit it one good time without really realizing it, its kind of hard to pinpoint where 15-20 miles went.

Nuke

Hand calculating is the only way to achieve any accuracy. In addition, 1-2 tank fulls doesn't give enough good representative data points to determine what your true average fuel mileage is. A 87 octane tune as compared to a 93 octane tune should not be expected to provide any economy unless your 87 tune was written explicitly FOR economy. And even then, don't expect more than maybe a 2-3 MPG gain, IF THAT.

There are so many variables that affect fuel mileage that I've quite frequently obtained up to 4 MPG difference driving the same 1000 mile stretch, stopping at the same gas stations, driving the same speed in the same manner. Don't think you can compare 1 or 2 tankfuls and get anything meaningful. Once you've hand calculated at each fill-up for about 4-6 months will you have enough data points to tell if subsequent data is indicative of something amiss.

tx_zstang

Depends on how you measure your MPG and the tune.
Fill up full, reset the odometer, drive, then next time you buy gas, fill up again, note the miles and gallons it took, simple math and you have true mpg.

The tune is only one part of the picture, but the driver is the other part.
Generally, my best MPG was with a custom tune on the highway, gaining nearly 2 mpg over stock, but over a couple of tanks on longer highway trips.

Driving around the city, a heavy foot will be hard to control, and that'll reduce mileage.

So you might be able to get some improvement, you might not.

Personally though, and maybe being a bit of an *** about it, if you're worried about mpg, get something different! Enjoy the Mustang or all it's worth and drive it like it was meant to be driven!! But then again, in reality, people do have to be concerned about mileage, and it's good to be able to get some kind of decent mileage from a Mustang.

Joshspony

I am all for people being aware of fuel economy, but really, if you gain a few mpg how much $$ are you really saving? If a person bought a CAI/tune just for mpg, how many fill ups would it take to pay that off?

Using real rough numbers, say you saved $5 a fill up, and bought a $550 cai/tune it would take over 2 years to pay that off at 1 fill-up per week. Personally I fill-up my car about every other week, with mostly daily driving.

Just my opinion, drive the mustang and enjoy it, don't put your foot on the floor very often and you'll do just fine on mileage. CAI/tune or not, if you drive like you stole it, your mileage will be s***y.

maxshuty

I'm an MPG nutcase. I do everything by hand calculations and measuring miles driven/gallons used etc.

I need the extra miles because I have to usually fillup 2-3 times per week because I commute 150 miles sometimes 3-4 times a week. So 20 miles actually makes a huge difference. Everytime I fillup I take MPG measurements. I know my car should ALWAYS get 300 miles per tank, and on 100% highway I should get 400 miles per tank. That is what I always got stock. Now I'm averaging less miles per tank than stock and using the economy tune and driving the car like a baby versus when it was stock I got on the throttle quite a bit and still managed 300/tank.

I have run the race tune (I'm running that right now) and obviously getting really crappy mpg, but on 87 eco tune I'm still getting the same MPG's as the stinking race tune is giving me and I screw around 100% more on the race tune. Trust me I do enjoy the Mustang for everything it is and I dont drive like a grandpa or something - I've got the biggest lead foot of anyone! But I'm wondering where this loss is coming from when we're talking about 100% highway driving measurements on cruise control. Basically what I'm trying to get at is could something be a little screwy with the tune (heck maybe they added an extra 0 somewhere that makes all the difference in the world or something, I dont know... lol)
I used to avg. 100 miles per quarter tank of gas - 100% hwy.
Now I am avg. 75 miles, and this is after several observations - not just one or two, probably close to 8-10 now. (I DRIVE A LOT... 25k miles I put on the car last year alone.)

svastano

Did you change oil recently and possibly put in heavier weight than it should be? Just a thought..

Sam

maxshuty

Changed oil with 100% synthetic oil good for 10k miles, 5W-30..
Fuel filter changed around 10k miles ago
New air filter (CAI)
Tires are fine
Tire pressure is fine
Weather is warm so that would if anything increase MPG
Wind is calm, no heavy winds I've been driving in
Just me in the car, no other people or luggage to contribute to extra weight
ONLY thing that has changed is the CAI+Tune and a Manual Mustang GT Muffler
Can't think of much else that would make a decrease...

sonicx

tried changing the spark plugs?... maybe the need a change. Holy Cow how much is on the clock of your car if you drove 25K last year?? As for the tune. Go back to stock if you haven't and then if you have a AM tuner i'd delete all custom tunes and then get a new custom tune and reload it.