Should You Be Buying Premium?

The Octane Question // Modern computer controls allow vehicles of every type and price to take advantage of high-octane gasoline.

- Eric Tingwall

The trend that’s changing the way America moves is far subtler than any good click-generating headline would have you believe. Electric vehicles are decades away from showing up en masse at country-music concerts, county fairs, and Tractor Supply parking lots. True go- anywhere autonomy will prove as elusive as finding satisfying vegan bacon. The trend we’re really living is the story of smaller engines working harder, in everything from family crossovers to six-figure autobahn barges. Downsized but hardly diminished, many of these shrunken engines are more powerful than their predecessors thanks to turbocharging, variable valve timing and lift, direct injection, and the advanced computer controls tying these all together.

Today’s engines are so sophisticated that even mainstream nonperformance vehicles can benefit from running on higher octane premium fuel. Vehicles such as the Ford Escape and Mazda 6 are advertised with power figures made on 93-octane fuel, although both companies are quick to note that these vehicles will happily run on 87. What automakers rarely say is what, precisely, are the benefits of paying for premium. That ambiguity can be expensive. Premium gas tracked at $0.59 more per gallon than regular unleaded as of this writing. In a vehicle averaging 25 mpg and traveling 15,000 miles a year, that amounts to a $354 annual surcharge for using the more expensive stuff.

Raising the octane rating (also known as the anti-knock index) doesn’t change the energy content of a gallon of gasoline. A higher octane rating indicates greater resistance to knock, the early combustion of the fuel-air mixture that causes cylinder pressure to spike. When higher-octane fuel is flowing through its injectors [see “Knock Knock”], the engine controller can take advantage of the elevated knock threshold and dial in more aggressive timing and higher boost pressures to improve performance.