UPDATE: This morning, AAA announced that Americans wasted $2.1 BILLION in 2015 purchasing premium fuel that their cars did not require. If you’re driving anything other than these 485 cars, stop spending extra money.
A .pdf with a complete list of all 485 2017 and 2016 models with a premium fuel requirement is at the end of this article.
Conventional wisdom suggests that the price of gasoline has plummeted since the dark days of 2009. But if you’re driving a car with a premium fuel requirement, your gasoline cost has skyrocketed in the last decade, to the point where it’s eroding a large percentage of the savings that regular fuel users have enjoyed.
And the list of cars that require — not just recommend — premium fuel grows every year.
What is Premium Fuel?
Simply stated, premium fuel has a higher octane rating than regular gasoline. Regular gas has an octane rating of 87, mid-grade or “Plus” is 89, and premium fuel typically has an octane rating of 91. Sometimes the rating can be even higher.
What is Octane?
It’s actually isooctane (C8H18), which consists of eight carbon and 18 hydrogen atoms, and it’s one of over 200 active ingredients in gasoline.
To understand why isooctane is a necessary active ingredient, you need to understand a bit about combustion.
Image Source: Colorado State University College of Engineering
Every car, truck, van and SUV sold in the United States that isn’t powered by diesel fuel or solely an electric motor has a four-cycle engine. The complete cycle of combustion begins — in this illustration — on the power stroke, when the spark plug ignites compressed fuel and air in the cylinder. That explosion drives the piston downward, turning the crankshaft, and opening the exhaust valve on the exhaust stroke.
As the exhaust valve closes, the intake valve opens, drawing new fuel and air mixture into the combustion chamber on the intake stroke. Finally, the compression stroke closes the valves simultaneously, compressing the fuel and air mixture until the spark plug ignites the mixture, beginning the entire process again.
Where isooctane comes in is during the compression stroke. It’s critical that the spark ignites the compressed fuel and air mixture at exactly the right time. But the heat of the engine and the compression of the fuel and air can cause “pre-ignition,” the ignition of the mixture without a spark at all. It causes knocking that not only is unpleasant to listen to, it’s inefficient and can damage the engine.
In the 1940s through the 1970s, fuel suppliers used tetraethyl lead to avoid pre-ignition, but rampant health concerns required its elimination by the mid-1970s. Instead, fuel providers used isooctane to prevent pre-ignition.
The octane rating isn’t actually the amount of isooctane in the fuel. To rate fuels, they’re compared against a mixture of isooctane, which resists knocking, and n-heptane, which is prone to knocking. If a blend of gasoline provides the same knock resistance as a mixture of 87 percent isooctane and 13 percent n-heptane, it gets an 87 Octane rating. If it has the same knock resistance as 91 percent isooctane and 13 percent n-heptane, it gets a 91 Octane rating.
Electronic Engine Management and Octane Ratings
Prior to about 1975, most cars on the road had carburetors unassisted by any kind of engine management technology other than the distributor. The distributor — as the name suggests — distributes spark to individual cylinders by sending high voltage to each spark plug through the plug wires. The time at which the distributor sends power to individual spark plugs — engine timing — is fixed in this type of system.
Engine timing could either be advanced or retarded slightly, but the system wasn’t smart enough to take advantage of changes in atmospheric pressure, fuel quality, octane rating or temperature. It’s one of the reasons why engines ran so poorly at higher altitude, and required different timing and carburetor jets to take advantage of the thinner atmosphere. Drag races in Colorado, for example, record much slower times than in places like New Jersey, that are essentially at sea level.
Engine management software connected to knock sensors took care of that. By the 1990s, your engine management system was sophisticated enough that even if your car had a premium fuel recommendation (we’ll get to why that’s italicized in a second), if there was a full tank of 87 octane in the fuel tank, the system could sense any pre-ignition, and could automatically retard timing to take full advantage of the fuel delivered.
You might not get the optimal performance or fuel economy that 91 octane could provide, but the car would run knock-free as long as you used a minimum of 87 octane.
Requirement vs. Recommended
Up until the last few years, just a handful of cars had 91 octane requirements versus 91 octane recommendations. High performance cars like the BMW M3 and the Audi S4 required 91 octane, and the engine management system was so calibrated toward high performance that running lower octane fuel was detrimental to the engine’s health.
That started to change in 2011 when Chevrolet introduced the Chevy Volt. It had a tiny 1.4-liter gasoline engine that worked as a backup generator to power the electric motor that sent power to the wheels. That engine had a 91 octane requirement, which meant that while you were saving fuel, you were spending more per gallon for it. Chevrolet noted that “in an emergency” you could run regular 87 octane in the Volt, but it would have a detrimental effect on the car’s fuel economy — its entire raison d’etre.
Since 2016, the Chevrolet Volt has eliminated the requirement for premium fuel.
The Smart ForTwo had a premium fuel “recommendation,” but it was a strong recommendation. If you wanted to realize the optimal combination of power and fuel efficiency from the tiny ForTwo, you had to run premium fuel. If you didn’t, you were driving a tiny automobile only suitable for two people that didn’t get much better fuel mileage than an ordinary subcompact sedan, with room for up to five, plus luggage space.
The issue now is that more and more cars ordinary cars have premium fuel recommendations, and they’re typically not “performance” cars, but vehicles that are helping manufacturers move toward the 54.5 mile per gallon average fuel economy requirement in 2025. If you’re not running premium fuel, you won’t damage the engine, but you won’t realize the car’s performance or fuel economy potential.
Dollars and Cents
As more and more cars enter the fleet with premium fuel requirements and recommendations, it means that the demand for premium fuel has increased, and with it, the cost of premium fuel has gone up.
At the pumps in Holliston, Massachusetts this morning, a gallon of regular gasoline cost $2.29. A gallon of premium was $2.83, an increase of $0.54 cents or a 23.6% premium over regular. While the U.S. Energy Information Administration expects the national price of gasoline to be lower this summer than at any point since 2004, the gap between regular and premium fuel has never been wider. In 2010, the national gap between regular and premium was just 9%, or $0.24 cents.
The result is that with a premium fuel requirement, you spend significantly more per year on gasoline. Take the information provided on every Monroney Sticker required on every new car as an example. The Annual Fuel Cost section is based on an average of 15,000 miles per year at an average price of $3.30 per gallon.
A car that gets 25 miles per gallon will consume $1,980 in fuel over 15,000 miles, using the $3.30 per gallon figure. Bump that up to $3.84 (the price differential we noted this morning), and it costs $2,304 per year — a difference of $324 per year.
Luxury Cars vs. Regular Cars
It’s true that many of the cars with a premium fuel requirement are luxury cars, or at the top of the performance spectrum. But there are many cars with a requirement that are attainable for just about any new car buyer.
Currently, there are 485 2016 and 2017 trim levels of vehicles that require premium fuel.
Audi has 49 different trim levels with a premium fuel requirement, many of which are in the range of the average price for a new car in 2016. The 2016 Audi A4, for example, starts at $37,300, compared to the average price for a new car, at $33,500.
BMW has 85 vehicles for sale with a premium fuel requirement, beginning with the least expensive car in its line, the $32,850 BMW 228i Coupe, which starts below the average price of a new car in 2016.
At the least expensive end of the spectrum, the $28,020 2016 Nissan Juke NISMO RS has a premium fuel requirement, despite only turning out 211hp, and a zero to 60 time of 6.7 seconds.
As its name suggests, the Volkswagen Passat V6 SEL Premium carries a premium fuel requirement, with a starting price of just $36,835.
We’ve compiled a PDF of all the cars available in 2016 and 2017 with a premium fuel requirement. Premium Fuel Requirement 2016 and 2017 model years.
Search for a new vehicle with BestRide.com’s comprehensive listings, beginning with this list of electric cars that don’t use fuel at all.