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Skidude 06-07-2012 11:03 AM

87 Octane
What happens if I put 87 Octane in my '05 OBXT? It's totally stock.

I only ask because I am thinking about taking a road trip to northern Canada, and there won't be anything else available. Will the stock computer dial back boost and timing to compensate, or will it just detonate and blow up the motor? How bad will my fuel economy suffer?

It would only be for a couple or three tanks.

P.S. Please don't suggest octane booster, I have researched that and it's not worth it.

BDII 06-07-2012 11:06 AM

Don't do it. Rent a car.

If anyone tells you otherwise, they are wrong.

Skidude 06-07-2012 11:10 AM

Well that's pretty definite... why won't the stock computer compensate? I know my mom's old 1.8t went 100k miles on 87 octane because she wouldn't listen to me about using premium.

BDII 06-07-2012 11:14 AM

your mom probably stayed out of boost.

You can run 87, but you will do damage when you get into boost.

There are too many factors that need to be adjusted when going from 91/93 to 87.

Fuel, timing, air... it's all too much for the ECU to compensate.

joelwatts 06-07-2012 11:17 AM

is it true that subarus are moreso finicky when it comes to fuel than other manufacturers?

bmx045 06-07-2012 11:19 AM

it's moreso subaru's knock control strategy. the engine has to knock before the ecu decides to do anything about it

No DRFT 06-07-2012 11:58 AM

Octane booster

Max Capacity 06-07-2012 12:16 PM

Keep the car out of boost !!!

The OEM map in the ECU is flawed at best with 91/93. If you like your XT and plan to keep it and do any hard driving, get it to a Tuner.

Now if you had Cobb AP or the cables for a laptop, and had a Tuner make you a 87 map I would think you could use that. But I'm no expert in going to 87 octane.

The best idea I've read here is, rent a car.

SCHM1AN 06-07-2012 12:19 PM

If you want to run 87 octane, get a regular OB, sans XT.

Are you going with any friends whose car you could take instead?

Nrw 06-07-2012 12:20 PM

You could always just try it and tell everyone what happens.

Disclaimer: I am not responsible for and damage to the car.

Spec B 06-07-2012 12:21 PM

If you stay out of boost you will be fine...but it will be a pretty boring road trip.

Skidude 06-07-2012 12:29 PM

Thanks guys, I won't put 87 octane in my car.

Have you people ever tried to drive these cars and "stay out of boost"? I hooked up a boost gauge for a week and it is ALWAYS in boost under any form of acceleration. It's amazing, and even with a boost gauge, I think it would be nearly impossible to stay out of boost without disconnecting the wastegate.

Spec B 06-07-2012 12:33 PM

On a seperate note - I am really surprised there is nothing higher than 87 octane in northern Canada.

Skidude 06-07-2012 12:40 PM


Originally Posted by Spec B (Post 3928049)
On a seperate note - I am really surprised there is nothing higher than 87 octane in northern Canada.

Not just Northern Canada... the James Bay Road:

Spec B 06-07-2012 12:42 PM


That is will be some trip...enjoy.

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