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Old 06-25-2011, 05:42 PM   #39
naimouasta
Scooby Specialist
 
Member#: 47998
Join Date: Nov 2003
Chapter/Region: Tri-State
Vehicle:
2002 WRX Wagon
2008 Legacy QSM

Default

where i usually get gas, there's a 10cent difference usually between 87, 89, and 91; but only 2-3 cent difference between the 91 and 93. i believe most places (if not all?) just bump the octane from 91 to 93 by adding ethanol. same with the places that have 92, they use ethanol to bump the 89 to 92 is my guess. the pumps usually say "up to 10% ethanol", so the amount is probably different depending on the octane.

i don't have a turbo so i usually just use 89, but my brother has a wrx. he gets a bit better gas mileage using the 91.

also i don't know anything about tuning but i read some thread a while ago where they had a higher injector duty cycle for 93 vs 91.
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