Octane question
Thread Starter
Registered User
iTrader: (3)
Joined: Mar 2008
Posts: 6,970
From: Upper North Bay
Car Info: '15 LE STI, '06 WRX White Wheeled Wagon, '06 B9
Octane question
So I was talking/arguing with my brother today.... here is the question
If you have the acn 91 map and run 100 oct gas will it hurt anything.
I know there is no horsepower advantage unless you have it tuned for 100 oct, but my question is will it physically hurt the motor.
I say no, my brother says yes, it will jack the timing up...
any insight?
If you have the acn 91 map and run 100 oct gas will it hurt anything.
I know there is no horsepower advantage unless you have it tuned for 100 oct, but my question is will it physically hurt the motor.
I say no, my brother says yes, it will jack the timing up...
any insight?
Thread Starter
Registered User
iTrader: (3)
Joined: Mar 2008
Posts: 6,970
From: Upper North Bay
Car Info: '15 LE STI, '06 WRX White Wheeled Wagon, '06 B9
but why would it matter its just higher rated octane, and correct me if i am wrong, but isnt the octane rating just a rating of the fuels ability to burn. so 100 octane burns easier and more controlled than 91 octane, so would there really be any problem?
Registered User
iTrader: (4)
Joined: Feb 2007
Posts: 2,644
From: SJ
Car Info: 94 Integra beater: one Slow 3 Series RIP EvoX
the rating is the fuel's ability to resist knock. the higher the number the more "anti-knocking" ability the fuel has.
Generally higher octane rated gasoline burns slower and will probably cause the car to be more sluggish. you might lose a few hp here or there but it should hurt the engine. You WILL notice crappy mileage though because the ecu will run the car rich once it's warmed up.
At least that's what I noticed and I switched back to 91 ASAP
Generally higher octane rated gasoline burns slower and will probably cause the car to be more sluggish. you might lose a few hp here or there but it should hurt the engine. You WILL notice crappy mileage though because the ecu will run the car rich once it's warmed up.
At least that's what I noticed and I switched back to 91 ASAP
iClub Silver Vendor
iTrader: (12)
Joined: Mar 2003
Posts: 8,228
From: 631 Railroad Ave. Fairfield, CA
Car Info: A Laptop
Running most 100 octane fuels or a mixture of 100 in a car that's tuned for 91 is not going hurt the engine. Like others have said, you may end up loosing a few hp because of the slower burn rate, but it will generally run smoother and have extra knock protection. It won't run any richer than your 91 map was running unless the specific fuel you use has a significantly different specific gravity. This is often the case in higher octane fuels, but most 100 octane tends to be similar to pump fuel.
FYI, I recommend to my customers to mix in a few gallons of 100 octane as an added safety measure when running the car under extreme conditions such as a very hot track day.
Thanks
-- Ed
FYI, I recommend to my customers to mix in a few gallons of 100 octane as an added safety measure when running the car under extreme conditions such as a very hot track day.
Thanks
-- Ed
Thread Starter
Registered User
iTrader: (3)
Joined: Mar 2008
Posts: 6,970
From: Upper North Bay
Car Info: '15 LE STI, '06 WRX White Wheeled Wagon, '06 B9
Registered User
Joined: Mar 2009
Posts: 226
From: Turlock, CA
Car Info: 2002 Impreza Outback Sport
Ill second this question, i'm running premium right now with no tune, haven't gotten the funds yet, so will 91 octane jack my stuff up when it runs on an 85 factory tune?
Registered User
iTrader: (4)
Joined: Aug 2008
Posts: 2,127
From: Livermore
Car Info: LUMPY CGM 05 WRX
My bad for being a ratard. "haha get the HANGOVER connotation there?"
Registered User
Joined: Dec 2009
Posts: 3
From: Cali
Car Info: 1995 2.5RS
Before worrying about washed cylinder walls or oil dilution, I would do a simple check on your spark plugs. That should tell you asap if 100 octane is too much for the car.
Check for excess carbon buildup or signs of incomplete combustion.
Check for excess carbon buildup or signs of incomplete combustion.
Thread
Thread Starter
Forum
Replies
Last Post
specb
Bay Area
17
Sep 12, 2006 01:56 PM
stealth-wrx
Engine/Power - EJ20T (pre-2006 WRX and JDM)
3
Feb 3, 2003 03:41 PM
meebs
Aftermarket Forced Induction - Turboed factory NA engines
4
Dec 11, 2002 07:06 PM
