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When Tracy Jackowski fills up her car, she pays no mind to the octane rating. The number that matters to her is the price.
“I use the cheapest gas there is,” the Sylvania woman said as she pumped Valero regular grade into her Chevrolet Malibu last week. “I don’t have a premium car. There’s not that much difference, I don’t think.”
The experts would tell her she's right. Most people don’t need to pay the extra 20 to 30 cents a gallon for high grade.
Premium gas is like coffee with a shot of espresso. It’s basically the same thing, just brewed with some extra potency.
In engines designed for it, higher-octane fuel delivers more power and can even help increase efficiency. But most cars aren't engineered to pull that extra juice out of the high-test.
“For 99 percent of the people, if your car says run on regular fuel, you’re not going to see any benefit running on premium,” said Roger Clark, the manager of General Motors Co.’s Energy Center.
Mr. Clark said it’s important to check your vehicle's owners’ manual to see what fuel the manufacturer recommends. If premium is required, you should follow the guideline. If it’s only recommended, you’re generally safe to fill up with whatever you want.
The grade of gas is set by its octane level. Essentially, the octane rating is a measure of the fuel’s ability to resist knocking, or premature ignition in a cylinder. In this part of the country, regular gas has an octane rating of 87, while premium is 91 or higher. Generally, higher compression engines call for higher octane fuel.
Most gas stations sell three or four levels of fuel. Manufacturers recommend mid-grade fuel for a handful of vehicles.
Across the market, about 17 percent of 2013 models require premium gas, according to data compiled by the automotive site Edmunds.com. Most of those are luxury or sports cars.
At GM, premium is only required in a handful of vehicles, most of which are high-end, high-performance machines such as the Corvette Z06 and the Cadillac CTS-V.
However, some luxury-oriented manufacturers such as BMW require premium across their lineups.
Keith Wallace, the service and parts manager at Yark BMW, said drivers should follow that guideline.
“The long and short of it, if the manufacturer says premium, you should use it. Nobody should go against what the manufacturer tells you,” he said.
Edmunds also says consumers should heed the advice of manufacturers who require premium in their cars.
However, experts agree that if your car doesn't require a premium diet, there’s no real need to feed it the petroleum equivalent of steak when hamburger will do.
“Really what this boils down to for most people is they can probably go to the lower grade of gasoline, save quite a bit of money, not damage their car, and not notice a drop-off in performance,” said Phil Reed, senior consumer advice editor with Edmunds.
Some manufacturers do recommend -- but not require -- premium fuel for certain cars, but Mr. Reed said it's unlikely most drivers will notice much performance difference by using it. Edmunds says premium is recommended for about 12 percent of 2013 model year cars.
Some people feel they’re treating their car by giving it an occasional tank of premium, believing it’s better for the engine and helps prolong engine life by cleaning out carbon deposits. Years ago, premium gas really was better, with additives and detergents not found in regular fuel. Nowadays, Mr. Reed said, every grade of gasoline has detergents and is of essentially the same quality.
That might explain part of the reason demand for premium gasoline has been falling in the United States.
Deliveries of premium fuel peaked in June, 1988, at 85,343 gallons per day, according to the U.S. Energy Information Administration. Demand has fallen fairly consistently since then, especially since the late 1990s.
In March, the most recent month with available data, the EIA said suppliers were delivering 31,717 gallons of premium fuel per day. Suppliers delivered almost 10 times as much regular gas that month, shipping 302,491 gallons per day.
Michael Leahy, an EIA analyst, said there’s not a strong consensus from analysts on why consumption has fallen, though better gas and new engine technology are likely contributors.
Knocking and pinging have been almost completely eliminated by knock sensors and other internal management systems that allow the engine to constantly adjust to make the most out of whatever fuel it's being fed. Other fuel-saving technologies, such as direct injection, can also reduce the need for premium fuels, GM's Mr. Clark said.
“When we design vehicles we design them mostly for regular [fuel], especially vehicles like a Chevy Cruize or a Malibu. Regular’s more prevalent, it’s more inexpensive, so we’re using all these new technologies to take advantage of that and not require you to use premium," he said.
Though manufacturers and others don't recommend it, even cars that "require" premium will often run OK on regular. However, under more extreme driving conditions, trouble could arise. Additionally, fuel mileage may drop with regular fuel, offsetting the money you save at the pump.
Price also may be a factor in the declining sales of higher grade gas. For most of the United States, the premium for premium has been hovering around 30 cents per gallon this year — a level first reached late last year.
However, on a percentage basis, the spread has been relatively steady since mid-2009, staying below 10 percent. In late 1990s the price premium was more than 20 percent.
The addition of ethanol into gasoline has made it less expensive to produce higher-octane fuels.
Mr. Leahy said that’s because of the addition of ethanol into gasoline. Raising the octane level of gasoline in the refining process actually lowers volume, making it relatively more costly to produce higher octane fuels.
The higher the octane, the bigger loss in production volume. But the ethanol that’s blended into gasoline has an average octane rating of around 115, effectively making it an octane booster and allowing refiners to start with lower-octane gas.
Contact Tyrel Linkhorn at firstname.lastname@example.org, or 419-724-6134.