Originally posted by yebo
karding,

sa US kaya walang benefit ang high octane kasi ang compression ratio ng engines dyan ay lower than compression ratios ng engines sa pinas. strict kasi ang emission controls dyan kaya pag tinaasan ang compression ratio, tataas din ang NOx levels kaya di pwede. so since mababa lang compression ration, di nyo need ang high octane gasoline. 87 ska 92 ron lang pwede na.

dito kasi sa pinas, 10+:1 na compression ratio ng ibang car engines kaya unleaded dito 92 ska 95 ron. tapos mga newer model cars talaga nakalagay sa owner's manual, 94 ron or better ang recommended fuel kaya forced-to-good kami sa premium.
sa East coast meron pang mga 94octane, dito sa west coast 91 na lang pinakamataas. Pero ang 91RON is only equivalent to 87octane. I read somewhere:

Most of the world uses RON (research octane number) for their octane rating. The US uses (RON+MON)/2 (MON = motor octane number) for octane rating (AKI.) The key item missing from the US ratings is the sensitivity = RON-MON. Sensitivity is around 10 typicaly.

To shorten the story US 91 octane rating assuming sensitivity of 10 should be close to RON 95-96
96RON nyo pala sa Pinas 91Octane namin sa US. Based sa readings ko, kaya mababa lang na 91 octane requirements sa high end cars dito (incl. my WRX) eh para di magastos sa gas, making the cost of ownership cheaper. Kse yung ibang Type R engine dito has a CR of 11.5:1 and still passes SMOG (emission test) just as long na may catalytic converter. Ngayon kung may ETHANOL na kahalo ang gas, malamang na mas mababa ang emissions ng auto. Kaya ko naman nabanggit na walang epek ang magkarga ng mas mataas na octane other than what the car manufacturer has recommended is because of this, to quote:
Higher octane gasoline will help my vehicle pass

One possible reason for the belief that higher-octane fuel produces lower emissions is that some brands of premium fuel contain alcohol as an octane enhancer. Ethanol has a higher octane rating than gasoline but it is the oxygen content of ethanol that affects the emissions, not the octane. The emission control system in your vehicle is designed to work effectively with the grade of fuel recommended by the manufacturer.