Naturally aspirated sports cars and turbocharged cars of all types are the primary sources of real, requisite demand for premium fuel.

Most cars, even luxury and upscale passenger cars, get along just as well on regular gasoline as on premium.

But now, even owners of cars that require the high-octane fuel are refusing to fill up with premium as prices approach $4.50 per gallon - more than 40 cents per gallon more than regular unleaded.

Demand for the 91-octane or higher fuel has fallen from 16% of the total U.S. fuel supply at its all-time high in 1997 to about half that, or 8%, in May.

The actual volume of premium fuel sold has fallen to its lowest level in 24 years, reports the Detroit Free Press.

“We’re down to the core, die-hard audience that believes they need 93 [octane],” said the publisher of the Oil Price Information Service, Tom Kloza.

The drop in demand comes despite an increase in new cars that carry a manufacturer recommendation or requirement for high octane fuel. In high-compression environments, like high-performance naturally aspirated or turbocharged engines, the higher octane helps prevent detonation, commonly called 'knock', which can cause extreme piston wear and engine failure.

Higher octane fuel does not enable lower-compression ratio engines to produce more horsepower, and can actually result in more unburnt fuel in some situations, reducing both power and fuel efficiency. Nevertheless, some motorists have persisted in using premium fuel believing there was some advantage to be gained. The massive drop in demand indicates many of those buyers are now returning to normal 87 octane fuel.