Excellent! New car for me (and my other CA brothers) in a few years from Subaru & Scion :thumbup:

I got 38mpg on the highway with 94 Octane E10 in my car. Just saying.

pretty much every dealer puts 87 octane in everything because they are careless morons. It isn't the best for the car but it won't really matter either. Once it's yours, put 91+ in. Before it's yours, just pretend all those crappy fillups never happened.

..... I live in Iowa..... Everything has ethanol


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I dont think 87 will hurt it at all, I had a 1994 Supra Stock motor, requires premium gas, I bought the car is 1998 and I only used 87 octane in it, runs fine and no knocks and I had over 200,000 miles on it when I sold it a few years ago.

But with the High 12.5-1 compression ratio i wouldn't use anything less than 89.

THIS is the correct answer.

Ditto! My step father works for Toyota at the National HQ in Torrence, CA, and is one of head parts managers. He stated the exact same thing as RYU did. Scion legally has to say only use whatever octane was used to get the performance and MPG numbers. It wont hurt the vehicle at all but could possible deminish performance and decrease MPG slightly. Everyone else are idiots and clearly have not done their homework. :slap:

With nearly 12.5:1 compression...Premium Fuel is the Only Fuel I will use.

Found some info in the manual published by Subaru on the BRZ.
●Use only gasoline containing a maximum of 10% ethanol.
DO NOT use any flex-fuel or gasoline that could contain more than 10% ethanol, including from any pump labeled E15, E30, E50, E85 (which are only some examples of fuel containing more than 10% ethanol)
●If you use gasohol in your SUBARU, be sure that it has an octane rating
no lower than 93 AKI.
●●SUBARU DOES NOT recommend the use of gasoline containing methanol

■SUBARU recommends the use of cleaner burning gasoline
Cleaner burning gasoline, including reformulated gasoline that contains oxygenates such as ethanol or MTBE (Methyl Tertiary Butyl Ether) is available in many areas.
SUBARU recommends the use of cleaner burning gasoline and appropriately blended reformulated gasoline. These types of gasoline provide excellent vehicle performance, reduce vehicle emissions and improve air quality

■Fuel types
Unleaded gasoline (93 AKI [Research Octane Number 98] or higher)
If unleaded gasoline with an octane rating of 93 AKI (98 RON) is not available,
unleaded gasoline with an octane rating of 91 AKI (95 RON) may be
used with no detriment to engine durability or driveability.

Thank you! Great Information! Clearly You did your home work!

If he knew what he was talking about he would have told you that anything under the 93 octane will 'definitely' diminish performance and also reduce fuel economy, not 'possibly'.
The engine is detuning itself to cater for the lower octane in proportion to the level it needs to go to avoid damage. It was never designed to run like that.
Have a word with someone in the service department instead of spare parts.

Has anyone got some dyno figures to show how much power is lost?

87 octane will not cause knock...but 87 octane is more prone to knock. This starts to become more serious as compression rises..and at 12.5:1 CR..its a number thats enough to worry about.

short term knock wouldnt worry me, and the ECU will pull enough timing to compensate. But its another matter that the wear and tear of the internal components of the engine are already accelerated before the car even has its first owner.

detonation is detonation regardless if its big or small, and id prefer to know that when i go into a dealer, the car is in tip-top shape.

87 octane in an engine that's built and tuned for 93 octane, especially with 12.5:1 compression ratio certainly will cause knock and almost certainly detonation if it's pushed with resulting piston failure.
The only saving grace is having knock sensors that dramatically retard the ignition and no doubt fuel too. Without that these engines would be toast.

Just read that dropping from 98/93 to 95/91 loses 5% torque due to the knock sensors retarding the tuning.
So we might speculate that 91/87 = minus 15% but I would imagine the loss for the lower octane would be even greater since the engine is going way outside it's design parameters.
There was a recent post where a new owner was disappointed with the performance of their new 86/BRZ and it might well have because the dealer put low octane fuel in it?

NO.