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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Below is a list of cars that you may not guess recommend or require premium fuel. The manufacturer's fuel recommendation from the owner's manual or consumer website is listed alongside each vehicle.
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 Volt
A 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."
2013 Lexus GS450h (hybrid)
Owner's manual: "Use of unleaded gasoline with an octane rating lower than 91 may result in engine knocking and significantly reduced performance. Persistent knocking can lead to engine damage and should be corrected by refueling with higher octane unleaded gasoline."
2013 Lexus RX 450h (hybrid)
The Lexus RX 450h is a luxury SUV that uses premium – not uncommon – but the non-hybrid RX 350 recommends regular gasoline.
Owner's manual: "Ratings achieved using the required premium unleaded gasoline with an octane rating of 91 or higher. If premium fuel is not used, performance will decrease."
2013 Mini Cooper (non-turbo)
EPA's Fueleconomy.gov: Recommended fuel: Premium
2012 Mitsubishi Outlander GT with 3.0-liter V-6
Owner's manual: "To get maximum performance, premium gasoline is recommended."
2013 Smart ForTwo
The 2013 Smart ForTwo can lose 3 mpg when running regular fuel instead of premium, according to Smart's how-to on maximizing ForTwo efficiency.
Owner's manual: "To maintain the engine's durability and performance, premium unleaded gasoline must be used."
From Smart USA's how-to on increasing the ForTwo's gas mileage: "The engine in your Smart ForTwo requires premium fuel for maximum fuel economy and performance." "Fuel economy using premium is approx. 3 mpg better than regular fuel."