What octane - TToTD

[dark steed]

07 GT/CS 4.6, I have put 94K of the 102K miles on it and hand calculate almost every tank. I put the CAI on a few months ago, before that it was stock airbox with a drop in K&N filter. (Someone can have it for shipping if you want it) Mileage improved slightly with the CAI/tune if I didn't rape it every time I drove it!

I just put 3.73 gears and all the internet guys say it should't affect mileage much either. My first full tank got 16.1 MPG, the worst by far. I averaged 19-21 mixed driving with 25 Hwy if I stayed under 75 MPH. My second tank isn't looking much better, maybe I am just driving it harder! LOL

 

[BruceH]

07 GT/CS 4.6, I have put 94K of the 102K miles on it and hand calculate almost every tank. I put the CAI on a few months ago, before it was stock airbox with a drop in K&N filter. (Someone can have it for shipping if you want it) Mileage improved slightly with the CAI/tune if I didn't rape it every time I drove it!

I just put 3.73.gears and all the internet guys say it should't affect mileage much either. My first full tank got 16.1 MPG, the worst by far. I averaged 19-21 mixed driving with 25 Hwy if I stayed under 75 MPH. My second tank isn't looking much better, maybe I am just driving it harder! LOL

It could also have something to do with how accurate the tire revs are too. The only way to get a good measurement is to measure and do the math. The manufacturer specs are rarely correct because they don't have the tire mounted on your wheel with your cars weight on it. I've seen as much as 20 revs per mile difference between what the manufacturer said and what I measured.

Just in case you aren't familiar with how to do it:

Measure tire height and multiply by 3.142. There are 63360 inches in a mile. Divide 63360 by the result of your prior calculation and you will have revs per mile.

 

[dark steed]

Thanks for the info, I once did a interstate test, in 75 miles it was 1/10 mile off with the markers (they are amazingly accurate, except at exits, etc). That was before the tune, I just manually changed the ratio after the gears...

 

[Captainstr8edge]

gears definitly affect mileage. easiest way is compare it to a gps. Do it with the odometer, manufacturers will often times purposefully show a higher mph than what you are actually traveling while the odometer is spot on. My motorcycle's speedo reads almost 10% high, It probably isnt that extreme but i wouldnt be surprised to see a 1-3% difference.

 

[Weou09]

gears definitly affect mileage. easiest way is compare it to a gps. Do it with the odometer, manufacturers will often times purposefully show a higher mph than what you are actually traveling while the odometer is spot on. My motorcycle's speedo reads almost 10% high, It probably isnt that extreme but i wouldnt be surprised to see a 1-3% difference.

Odometers can also be off due to a tire change/gear change. My '12 Tacoma was about 1/8 mile short per mile because of the larger tire.

 

[BruceH]

Thanks for the info, I once did a interstate test, in 75 miles it was 1/10 mile off with the markers (they are amazingly accurate, except at exits, etc). That was before the tune, I just manually changed the ratio after the gears...

That's doing pretty good imo. I use a calibrated 5 mile stretch of interstate to back up my calculations.

Do you know what tire revs are in your tune? IIRC Ford used 762 on stock 05-09 Mustang GTs. I'd have to look it up in Advantage to be absolutely certain.

 

[dark steed]

I used my GPS on the way to the airport today, and it was off 1/10 in 6 miles, not enough to cause 3-4 mpg error, more like .3. Maybe I just need to slow down....
I will measure the tire height when I get home.
I presume that you can adjust the revs/mile on a SCT/Bama tuner?