It's common to see "requires 91 octane gasoline for best performance" on the fuel door of sports or luxury cars. So, we scratch our heads when we see the same premium recommendation on a family car, hybrid or non-performance car. According to AAA's FuelGauge Report, the price difference between regular and premium gas is 32 cents nationally. Spending an additional $4.80 on a 15-gallon refuel isn't an insignificant amount of money, and you could save it if you buy a similarly efficient car at a similar price that runs on regular gasoline.
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Truthfully, most cars can run on regular gasoline even when they "recommend" premium. It's the "requires" premium you'll have to watch out for and read the owner's manual fuel requirements carefully. A modern engine's computer can compensate for lower octane gasoline to run the fuel safely, though there's typically a tradeoff in performance and fuel economy.
High-compression engines and engines using superchargers and turbochargers are more susceptible to engine knocking and need higher octane fuel to keep fuel burn in control. Usually relegated to performance and luxury cars, high compression engines and turbochargers are finding their way into more pedestrian cars because in many applications they increase the efficiency of smaller engines.
2013 Acura ILX Hybrid Owner's manual: "Unleaded premium gasoline, pump octane number 91 or higher. Use of lower octane gasoline can cause occasional metallic knocking noise in the engine and will result in decreased engine performance. Use of gasoline with a pump octane less than 87 can lead to engine damage."
2013 Chevrolet VoltA GM representative has told us the Volt can run on regular in an emergency, but premium should be used for maximum fuel economy and performance.
Owner's manual: "Use premium unleaded gasoline with a posted octane rating of 91 or higher. If the octane is less than 91, you could damage the engine."
2013 Dodge Dart Aero with turbocharged 1.4-liter Dodge's most-efficient Dart trim level is the Aero that has a 41 mpg highway rating with a six-speed manual transmission and turbocharged 1.4-liter engine. The Aero has some aerodynamic features that other turbocharged Darts don't, and when running on premium gas, this specific model delivers the 41 mpg estimate.
Owner's manual: "This engine is designed to meet all emission regulations and provide satisfactory fuel economy and performance when using high-quality unleaded regulargasoline having an octane rating of 87. For optimum performance and fuel economy the use of 91 octane or higher is recommended."
2012 Fiat 500 (non-turbo)Owner's manual: "Your vehicle is designed to meet all emission regulations and provide satisfactory fuel economy and performance when using high-quality unleaded gasoline having an octane range of 87 to 91. The manufacturer recommends the use of 91 octane or higher for optimum performance."
