Originally Posted by Defiant Autospeed
93 is not "optional" Its a turbocharged vehicle. 91 is the MINIMUM, and its only called the "minimum" because it will "work" without breaking pistons bone stock. Realistically, if you want to protect the health of your motor, 93 is the minimum. And you WILL make more power on 93 than you will on 91. Subaru's turbocharged cars, show repeatable gains with zero tuning up to around 100 octane. So yes, its most defintely not pointless. The difference between 91 and 93 is a big chunk of timing. Timing that makes power.
86-87 is actually harmfull to the engine. Dont take my word for it, open the gas cap and look for the lable or read the manual. Or take myword for it. I have seen the pistons out of a motor that ran 87 for about 20k miles, the tops of the pistons looked like you hit them with a 12gauge shotgun there was so much damage from detonation.
And I know why people ask this question, and no offense but its about the dumbest logic you can use.
Here is why.
The difference between 87 octane and 93 octane is about 20 cents.
An average fillup will be about 11 gallons.
SO we are looking at a difference $2.20 per tank of gas.
The average person will fill their tank up 4 times a month.
SO we are looking at a difference of $8.80 a month.
4 times a month, times 12 months means 48 fillups.
Lets just give it the benefit of doubt, and say 60 fillups.
The HUGE savings, the life changing, make or break your ability to pay your bills by using cheap gas, is
$132 a year.
If you cant afford that, you cant afford a car with a pricetag higher than about $1500 or so.
$132 a year savings, if you use 87 octane. F0r that $132 that you save, you get to have a good solid 20whp less, if not 30+ less. (Remember, that HP number that Subaru advertised on your car, was done on clean 93 octane) You also get constant low level detonation that slowly erodes your pistons, slowly lowering compression.
And like I said, your ECU will keep giving you more timing up to around 100 octane. WHich means, there is power to be had, with ZERO tuning, by using up to around 100 octane fuel.