1.   Further, prices are often higher still in big cities like Chicago, where government requires cleaner gasoline as a pollution-control tool.

2.   It does, however, require premium gasoline.

3.   New ethanol plants are popping up across the Corn Belt after the Bush administration decided in June to continue requiring oxygenated gasoline in California.

4.   The rule requiring cleaner gasoline will make it easier for the car manufacturers to meet their new targets.

5.   In standard gasoline engines, fuel and air are mixed outside the cylinder so the mixture is the same throughout the cylinder, requiring more gasoline to air.

6.   The Bush administration will not exempt California from a rule requiring that gasoline contain clean-burning additives such as corn-based ethanol.