Only 5 percent of new vehicles sold in the U.S. require premium gasoline, the AAA says, but the higher-priced petrol accounts for 20 percent of total fuel sales nationwide.
Are you among the motorists buying premium because you think it benefits your car's fuel economy and performance, even though the vehicle owner's manual says you only need regular?
If so, experts - including Car and Driver magazine, the Consumers Union, the Federal Trade Commission, and Tom and Ray Magliozzi, the Car Talk guys from National Public Radio - say you are simply wasting money.
And with gasoline prices at all-time highs - regular unleaded spiked to $2.069 per gallon in the Toledo area a week ago and the national average for unleaded regular
topped $2 per gallon for the first time ever this week - the extra approximately 20 cents per gallon that premium can cost is an unnecessary luxury.
For most cars designed to run on regular, "you're not gaining one iota by putting premium in them. You're just wasting money," said Gabriel Shenhar, the senior auto test engineer and special publications program manager for Consumers' Union, the publisher of Consumer Reports.
A few vehicles may gain "marginally" increased engine power if they're filled with premium, he told The Blade, but "most people won't know the difference."
According to the Federal Trade Commission, using an octane grade higher than recommended in a vehicle's operations manual "offers absolutely no benefit.
"It won't make your car perform better, go faster, get better mileage, or run cleaner," according to the FTC's "Low-Down on High Octane Gasoline. "Your best bet: Listen to your owner's manual."
The Magliozzi brothers note that unnecessarily high octane is widely believed to increase pollution from cars, rather than reduce it. The notion that "treating" a car to premium gas is "hogwash," they say.
The exceptions? Big sport-utility trucks, luxury cars, and anything else with a high-performance engine. For those vehicles, the owner's manuals are clear: Premium is recommended and cost-cutting to a cheaper grade can cause reduced engine performance.
A Car and Driver test of five vehicles - three of them calibrated to run on regular, two for which premium was recommended - found negligible improvement when the "regulars" were fed premium. The high-performance BMW and Saab models in the November, 2001, test ran with measurably less power when fed regular, but neither suffered any "drivability problems."
While Mr. Shenhar said explaining the decision by a majority of premium buyers to purchase the higher-priced gasoline "probably requires an answer from a psychologist," two forces appear to be at work.
For one, gasoline advertising has tended to emphasize cleaner running and better performance from premium. But the FTC said all gasolines now are required to contain detergent additives to eliminate the build-up of engine-fouling deposits.
Spokesmen for Marathon-Ashland and Sunoco both said yesterday that their companies recommend motorists buy the grade of gasoline recommended in their owner's manuals. BP-Amoco, which for several years pitched its premium gas during the winter as having an additive to combat gas line freeze-up, now offers that additive in all of its winter gasolines.
The other factor at work here appears to be more historic in nature. Years ago, premium really did boost engine performance because the higher octane content helped control knocking and pinging, which occurs when the air-fuel mixture in an engine's cylinders becomes over-pressured and explodes prematurely. The higher octane raised the temperature at which such explosions occurred.
Older, high-performance engines in muscle cars of years gone by could actually be damaged by continual knocking and pinging attributable to inadequate gasoline octane. But spokesmen for several automakers told The Blade knock sensors in modern engines automatically adjust cylinder timing, so that is no longer a problem.
If engine knock does develop and is allowed to persist, engine damage remains a possibility. In that case, manufacturers say, it's usually a sign of an engine in need of a tune-up.
"With today's electronic engine controls, it's unlikely you would have engine damage [from using regular]," said Ford spokesman Mike Vaughn.
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