Highlights from the article:
Marti Mayne once fueled her low-octane Subaru with high-octane gas. When prices dropped earlier this year, she stuck with cheaper fuel because "I don't think that my car runs any differently on high, medium or lower grade."
She's right. Engines designed for regular fuel don't improve on premium and sometimes run worse. And today's engines designed for premium run fine on regular, too, their makers say, though power declines slightly.
Prejudice and preference aside, engineers, scientists and the federal government say there's little need for premium.
All Porsche engines are designed for premium, too, but it's not available everywhere. "Our cars must be able to drive all over the world, and so we are able to run on regular," says Jakob Neusser, director of powertrain development at Porsche's research and development center in Weissach, Germany. "You don't have to feel that a mechanical problem or anything else will happen" using regular gas, even in the highest-performance, regular-production Porsches.
Premium, in fact, sometimes is worse fuel than regular. It resists knock because it's harder to ignite than lower-octane fuels. As a result, some engines won't start as quickly or run as smoothly on premium, notes Gibbs, the SAE fuel expert.
High-test does have a potential fuel economy benefit. It is slightly denser than lower-octane gas, meaning there's a little more energy in a gallon. But the small difference is hard to measure in real-world use, and that same density can contribute to undesirable buildup of waste products inside the engine.
No data show that engines designed strictly for regular run better or longer on premium.
"There is no gain. You're wasting money," insists Jim Blenkarn, in charge of powertrains at Nissan in the USA.
By James R. Healey, USA TODAY
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