Why would the exact same car call for gasoline with a different octane reading in Canada?

Dear Tom and Ray:

My husband and I rewarded ourselves with a 1994 Lexus GS300 for our 50th wedding anniversary. The owners manual calls for premium gasoline. But my husband has a question. The same car in Canada does not require premium gasoline. Why the difference?

RAY: Sorry it took us a few months to answer your letter, Joan, but we had to send my brother up to Canada in his 1963 Dodge Dart to investigate this personally.

TOM: And I would have been back sooner, but unfortunately, I had a little car trouble at the border.

RAY: The border of EVERY STATE he passed through.

TOM: From what we can tell, the American GS300 and Canadian GS300 are exactly the same. Both cars have engines that are equipped with knock sensors, which compensate for a low octane fuel, and adjust the engine's timing accordingly. Both cars are engineered to produce optimal performance on high octane fuel, but CAN run on lower octane fuel without doing any damage to the engine.

RAY: And that information is reflected in both owner's manuals. The American manual tells you to "select premium unleaded gasoline with an octane rating of 91 or higher for optimum engine performance." However, if premium unleaded is not available, the manual says you can temporarily use regular unleaded.

TOM: The Canadian owner's manual says exactly the same thing, except it ends each of the sentences with "eh?"
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