Quote:
Originally Posted by Isaac Zachary
Where octane is important is at higher engine loads, like when you have the pedal to the metal. But shifting from 4th to 3rd at part load because of using the recommended octane instead of high octane fuel for forced induction engines sounds fishy.
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High engine load can occur at any rpm. Also, high engine load at low engine speed is more prone to pre-ignition because the air/fuel mixture has more time to heat up before the spark.
Given that these are hybrid vehicles also means that the ECU is always trying to run the engine moat efficiently, high load and low engine speed. While the vehicle is rated for 87 octane, it does benefit from more knock resistant fuels.