Higher octane gas can allow for improved engine efficiency, but actually making such a widespread change in the US looks rather tricky.
Whether you call it "premium," "super unleaded," or even "high test," it all means the same thing -- the most expensive gasoline at the pump. In a somewhat counterproductive trend, the skyrocketing cost of fuel is forcing automobile manufacturers to use smaller and more powerful engines, often with forced-induction. Unfortunately, these engines require higher octane... the distinguishing feature of premium fuel.
It's easy to take gasoline prices for granted when it comes to NASCAR, but the high-octane fuel used by competitors burns quickly under race conditions, drawing on some 6,000 gallons of fuel in a weekend. Supposing gas is at $2.83 a gallon, which is about the going rate for regular in many U.S. cities, that means that gas for a race weekend comes out to about $17,000... and that's assuming pump gas - NASCAR motors run on far more exotic (and costly) 110-octane leave-in-the-lead hooch.