When regular gas spiked over $4.00 per gallon here, and 91 octane went well past $4.50 a gallon I decided I'd run 89 (mid-grade) and see what happened.
NOTHING different and nothing changed.
As we all know: 0ctane does not equal horsepower
No pinging, no detonation, nothing. Runs exactly the same as when I used 91.
I would never question using 89 octane.
I am not in an area where extreme temperatures or altitudes are common.
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2008 WR250X
Gearing: 13t - 48t
Power Commander 5 / PC-V
Airbox Door Removed - Flapper glued - AIS removed
FmF Q4
Bridgestone Battlax BT-003rs