If you drive a fancy car, you've probably noticed you're paying even more lately for the privilege.
The nationwide average price difference between regular and premium unleaded gasoline reached 30 cents per gallon for the first time in 2012 and has stayed at or above that level so far this year, according to data released this month from the U.S. Energy Information Administration.
The price spread has climbed steadily from 18 cents in 2000, peaking at 33 cents in January.
Regular unleaded has an octane rating of 87, while premium boasts octane levels of 91 to 93.
In Oklahoma on Thursday, premium fuel users paid on average 27 cents more per gallon than regular consumers paid, according to AAA's fuelgaugereport.com.
For cars designed for regular, there is no advantage to using the more expensive fuel. Engines that call for higher-octane fuel are more likely to knock if the octane level falls too low.
Higher-performance engines are more likely to call for the more expensive fuel. Typically those are found in sports and luxury vehicles.
The rising price of higher-octane fuel has to do with changing fuel blend processes, according to the government report.
Refiners previously used MTBE to raise octane levels, but the Energy Policy Act of 2005 banned the chemical because it was found to cause cancer when it leaked into the water supply.