#24: Dr. Octane
November 12, 2010
Today’s rather than answering a specific reader question, let’s rebuke a common misperception that comes up every few days on every scooter forum:
My (dealer and/or manual) told me to use premium gas in my Asian scooter.
Dr. Buzz: First, you have to understand that “Premium” is a bad name for gas, because it’s not BETTER, it just has different properties that work better in certain engines. For that matter “High-Octane” doesn’t even mean “more octane,” the Octane rating simply quantifies the anti-knocking characteristics of the fuel. If those Wikipedia links are too intense for you, here’s The Straight Dope.
So if your scooter manual specifies 92 octane, you should use it right? Probably not. Your manual is likely full of mistranslations, typos, “Engrish” and sloppy conversions. For instance, I’ve seen Chinese and Taiwanese manuals simply translate the word “km” to “miles” without actually changing the numbers!
Octane ratings aren’t metric, but Taiwan and most other Asian counties use RON octane ratings and the US uses AKI octane ratings. At any gas station in Taiwan, you’ll see 92, 95, and 98 RON octanes available. 92 is the lowest rating available there. In the US, you’ll find 87, 89, and 91 AKI octane, where 87 is the lowest rating.
If that’s not enough proof, here’s some actual math:
RON Octane Rating x 0.95 = AKI Octane Rating,
So 92 x .95 = …you guessed it, 87!
In some cases, using higher-octane-rating gas than specified is actually bad for your engine. And it’s certainly costing you money.
But what about the people who insist they’re getting better mileage or higher top speed with high-octane-rating gas? Ask them to see their dynamometer readings from tests performed under scientific conditions They’re either lying, deluding themselves, or crediting one of the dozens of factors that influence mileage and top speed to their gas.
Do you have a question for our so-called experts? Email Dr. Buzz! Your confidentiality is guaranteed, to the degree that we’ll spell your last name with one letter.
Note: Dr. Buzz is an unlicensed, mostly-fictional doctor. Take his advice with a grain of salt.