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With gas prices on the rise and the difference between midgrade and premium being around 40-50 cents, anyone out there running midgrade or alternating between 89 and 93? Can you feel hp decrease, or any pinging or knocking?
 

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With gas prices on the rise and the difference between midgrade and premium being around 40-50 cents, anyone out there running midgrade or alternating between 89 and 93? Can you feel hp decrease, or any pinging or knocking?
What does your manual require? If it’s 91 you should not be putting anything less in it unless it’s an emergency.

You don’t notice the pinging and detonation usually until it’s too late.
 

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Subaru is not really consistent with their wording when it comes to this subject.

From the 2016 brochure:
“Premium unleaded gasoline recommended (91 octane required for STI, 93 octane for maximum performance).”

From the 2017 brochure:
“Premium unleaded gasoline (91 octane) is required. 93 octane recommended for maximum performance.
WRX only: Regular unleaded gasoline, 87 octane may be used.”

From the 2018 brochure:
“Premium unleaded gasoline (91 octane) required. 93 octane recommended for maximum performance (WRX STI).”


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It's amazing that brochures still exist. Wow!

I'd recycle those and use only the owner's manual that came with your car as a reference.
 

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its a turbo, its summer time. If you use 87/89 in boost in 90 deg weather the engine will knock like the Navy on your Moms door during shore leave. If you want your car to last and not blow up, use the correct grade fuel.
 

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If you want to run lower octane you could always tune for it.. retard the timing some and decrease boost. I don't know what kind of car you have, but the turbo ej engines are fairly low compression, so with a detune they shouldn't have much trouble handling lower octane. Not sure if that fits your money saving agenda though.
 

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Subaru is not really consistent with their wording when it comes to this subject.

From the 2016 brochure:
“Premium unleaded gasoline recommended (91 octane required for STI, 93 octane for maximum performance).”

From the 2017 brochure:
“Premium unleaded gasoline (91 octane) is required. 93 octane recommended for maximum performance.
WRX only: Regular unleaded gasoline, 87 octane may be used.”

From the 2018 brochure:
“Premium unleaded gasoline (91 octane) required. 93 octane recommended for maximum performance (WRX STI).”


Sent from my iPhone using Tapatalk Pro
The discrepancy here is that the CVT cars can run regular. The manuals need the good stuff. When in doubt check your gas cap. Theoretically if you were dead set on running regular, you could add meth/water injection and be good to go. However as others have stated, dont be stupid. .50 per gallon is a lot cheaper than an engine replacement.
 

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Have you considered trading the car for a Honda Civic or other economy car that can run on 87 octane gas? You may see an increase in gas mileage and you will reduce the likelihood of an engine go boom episode in the future.
 
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