As strange as this question sounds, this is a common and long-standing practice among many motorists who consider an occasional tank of premium a special treatment that will help their engines last longer.

The basis for this assumption is that a tank of higher octane gasoline, maybe because it costs more, will somehow reduce engine wear. The assumption is fundamentally incorrect, though an occasional tank of premium may help an engine in other ways.

Know what octane your engine needs

An engine's design, which includes such factors as its combustion ratio and its operating temperature, is related to something called an octane rating. Usually, we think of an octane rating as something that applies only to gasoline, but the engine itself has such a rating that represents the minimum octane level that the engine requires for proper operation.

An engine needs a minimum level of octane to avoid ping, which is caused by uncontrolled combustion of fuel inside the cylinders. Excessive ping can severely damage the engine. The octane rating on the gasoline is a measure of its anti-knock or anti-ping properties.

Engine controls to the rescue

If your car does not ping on regular, then there is no reason to seek a higher-octane gasoline. The anti-knock level of the regular in this case is adequate for the engine. And today's advanced engine controls adjust the engine's timing and fuel mixture to compensate for differing octane levels to prevent pinging or knocking.

Many cars only require regular gas, however, vehicles with smaller turbocharged engines and the powerplants of higher performance vehicles will have higher factory recommended octane levels. That doesn't mean your car won't run on anything less than the 91 octane recommended by the manufacturer. Rather, you won't get the same performance or fuel economy if you use a lower grade gas.

The bottom line

Even if you car runs on regular, an occasional tank of premium isn't a bad idea since often these fuels have a higher-quality additive package put in at the refinery. The actual additives in a particular brand of gasoline are generally not disclosed by refiners. But usually they include detergents and other solvents that keep the fuel system clean. 

But in the long run, stick the the manufacturer's recommended octane level--if you requires only regular, you'll save money without putting your car's engine at risk.

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