premium grade gasoline

基本解釋

Usually, switching to the mid-grade or premium-grade gasoline will remove the knock.
通常，切換到中等或以超值的汽油會刪除敲。

According to the EPA, a motorist who drives the Volt exclusively on electric power will pay an estimated 4 cents per mile in energy costs, while one who never recharges the battery and runs the car exclusively on gasoline (with premium grade required) will pay 9 cents per mile.
FORBES: Living With A Chevrolet Volt
It takes a double-size margin on premium gas, but the highest grade represents only 2% of its gasoline sales, versus 7% industrywide.
FORBES: Inconvenience