Nuke

Todays fuels are formulated pretty well throughout the octane range; not like years ago when you needed higher octane to help burn off deposits. Other than a few minor single digit HP gain with higher octane and no custom tune to support it, higher octane only lightens your wallet. Any perceived fuel mileage improvement is likely your mind having false hopes.

Matt's 95 Stang

Nuke I do have a tuner and unlimited tunes from BAMA that is why I am asking about increasing my oct to something higher (say 91).

Matthew

Nuke

What octane tune are you running now? You'll likely NOT see any change in fuel mileage; at least not enough to offset the higher fuel cost. But you might like the added HP increase.

Matt's 95 Stang

Right now 87R. Hmmm.....more horsepower.....no. That doesn't interest me

Matthew

hogasswild

I didn't know Bama made a race tune for 87 octane. Is that new? I thought you could only get street or performance.

13V6coupe

Well call mine an anomily then but if I run 87 octane I get atleast 2 mpg less than when I run 91

Doing the math it is pretty much a wash on weather you save any money or spend any extra money to run 91.

Locally;

87=3.579 @ 30 mpg highway............11.93 cents per mile
93=3.799 @ 32 mpg highway............11.87 cents per mile

87=3.579 @ 26 mpg combined..........13.77 cents per mile
93=3.799 @ 28.5 mpg combined.......13.33 cents per mile

mileages tank to tank vary a little bit, but at 5,500 mile thus far these are pretty common for me.

I drive right past the BP with 93 octane 4 times a week during the summer so it isn't out of the way to get it either and the car feels snappier too. I have not driven it since October due to winter snow, salt and stupid drivers spinning out regularly.

The station by my house (kwiktrip) that sells 91,89,87 I don't see any difference in mileage or driveability running any of them, so then it makes no sense (I suppose) to pay the extra 7 cents for mid grade or 22 cents for premium.

157dB

What?
Why the need for the 91 STREET/RACE tune for
being such a grandma driver?

Grandma driving will give you the best MPG no
matter what tune you use. 91 is more $$ than the 87.
Are you trying to save as much $$ as possable
or are you trying to just get the best MPG no
matter what the fuel costs per gallon (87 vs 91)?

Remove two of the injector power plugs.
That will give you the best economy.
Just feed 4 cylinders instead of 6.
Maybe a device that drops a cylinder at random as you drive...
Maybe you need one of those Smart Cars...
Do you have a TB spacer? Thats worth 2 MPGs right there...

TRexGAWD

In my opinion the only time you'll see a bump in MPG is by using ethanol free fuel.. Where I live we have Pur stations that are 93 octance ethanol free.. It does cost more (about 40 cents per gallon) so you're not saving anything but I noticed a solid 3-4mpg increase in my day to day driving.

Nuke

And my opinion, too. I have 1 1/2 years of highway driving (900 miles round trip every 2 weeks) data using both ethanol free and ethanol laced fuel. 3-4 MPG was the average difference.

locoone

The only way to tell is to run a minimum of 3 tanks of each while keeping written records and see for yourself. always filling the same brand.
I've had cars it didn't make a difference and cars it did (ethanol fuel always got crap mileage by 4-7mpg below what straight gas gave). the last 07 focus I had actually got a solid 5+ mpg running premium over 87 on the hwy.
My tahoe you can **** in the tank and it will burn it and not make any difference in mileage.
So far on the 13 running premium only averages about 2mpg better on the hwy. but it still needs some break in mileage put on it yet and with 3:31's I don't expect much. It however hates ethanol and it does show a pretty decent decrease in mpg.