With the typical new passenger vehicle costing more than $33,000, American drivers understandably want to do everything they can to preserve their investments.
And what better way to do that than by spending a few extra cents per gallon and occasionally treating your car to a tank of premium fuel?
Don’t do it. Unless one likes to unnecessarily enrich the oil companies, there is no reason to buy premium gasoline for a vehicle that needs only regular.
According to a report this week from AAA, 16.5 million drivers used premium fuel on average at least once a month over the last year, although their cars required only regular grade gasoline, accomplishing nothing positive and wasting $2.1 billion.
There are advantages to using brand-name fuels, whose detergents and additives can help engines run cleaner and last longer. (More on that below.)
But using a higher octane fuel than a vehicle’s owner’s manual specifies “provides no increase in fuel economy, horsepower or a reduction in emissions,” said Greg Brannon, the AAA’s director of automotive engineering.
Unless you have a high-performance car — like a BMW M3 or a Jaguar XF — whose engine is designed to require the use of higher octane gasoline, so-called premium gasoline, your engine will let you know if regular gas isn’t good enough.
How? By making a metallic pinging or knocking sound when you accelerate. If that doesn’t happen, feel free to fill your tank with the cheaper stuff. As the Federal Trade Commission’s website so succinctly states: “Unless your engine is knocking, buying higher octane gasoline is a waste of money.’’
Gasoline sold in the United States usually is available in three octane ratings: Regular gas is typically 87 octane, midgrade is 89 and premium might be 91 to 93.
The difference is not mere marketing. The higher the octane number, the greater the fuel’s resistance to detonation. Decades ago, that mattered. Using a lower octane fuel could often result in pinging or knocking because the fuel was igniting prematurely. Knocking is not good because it can cause premature engine wear.
In the 1960s, vehicle engines were so sensitive to knocking that one fuel company, Sunoco, offered eight octane grades at the pump. And the company produced a chart, second only to the periodic table of elements in complexity, to help drivers figure out which blend their make and model car required. (It being the ’60s, the only cars listed came from Detroit.)
Back then, too, gasoline also contained tetraethyl lead to dampen knocking and increase octane. But leaded gasoline, a neurotoxin and environmental hazard, was eventually outlawed.
Modern engines not only don’t need lead but have sophisticated antiknock technologies that sense a fuel’s octane rating and adjust their ignition timing to prevent damage.
A vehicle’s owner’s manual specifies the type of fuel required for proper performance, although it might also say that premium fuel is ‘‘recommended.’’
When premium fuel is merely recommended, there is no reason to use it instead of regular, according to Jake Fisher, Consumer Reports’ director of auto testing.
In its own experiments, Consumer Reports found that vehicles that “recommended” premium did not increase acceleration or fuel economy compared with regular gasoline.
At Ford Motor, all vehicles are designed to run on regular fuel, with the exception of high-performance models like the Mustang Shelby GT350 and the Focus RS, which have high-compression engines that burn hotter, said Steve Russ, the senior technical leader for internal combustion engines at Ford Global.
And at General Motors, premium gas is required only in vehicles like the Chevrolet Camaro ZL1 and the Corvette Z06, with their supercharged 6.2-liter V8 engines. Even the big Cadillac Escalade recommends, but does not require, premium fuel.
In fact, more than 90 percent of the company’s products are calibrated for regular gasoline, according to Bill Studzinski, G.M.’s engineering group manager for fuels. “We have always said, ‘Don’t put more octane in your tank than the owner’s manual requires,’” he said.
Ford and G.M. agreed that there was one exception: If a vehicle was used to pull a heavy load or operate in extremely dry conditions, “you might gain a little in performance” from premium, Mr. Studzinski said. “Generally, there’s not a big benefit.”
Right now, the best way to ensure that your car is getting its best fuel economy is to use gasoline that helps keep the engine clean. To maintain an engine’s life and performance, it is important to prevent deposits from building. Deposits can reduce fuel economy, cause hesitant starts and increase emissions.
But it is the quality of the fuel, not its octane rating, that matters. That is why the brand of gasoline you buy could make more of a difference than the octane grade.
While most gasoline is refined by a handful of major players, the quality depends on what ingredients are ad