Richard Russell answers this small,but thought provoking, question at The Globe and Mail, revealing the small–but real–regulatory differences between Canada and the United States.
Shell, for example, uses more volatile fuel here in winter “to provide better cold starts and driveability.” Shell and other mainstream refiners are constantly adjusting their fuels on an almost weekly basis, one of the reasons I am constantly recommending the use of fresh fuel.
The fuels also differ geographically. Shell typically only uses ethanol in regular grade fuels, in specific markets including the Lower Fraser Valley and Southern Ontario; ethanol is used in all regular grade fuels in the United States, regardless of the refinery of origin.
Octane ratings for regular, mid-grade and premium Shell fuels across Canada are 87/89/91. In the United States, an 85-octane fuel is available in some markets of higher elevation such as the Rockies and premium ratings for premium can range from 91 to 93, depending upon the market.
Shell says that there are environmental differences between the regulations as well. “The federal limit on benzene in gasoline is currently lower in Canada than the U.S., so our levels of benzene are lower; typically we are also lower in sulphur content than in the U.S.”