A web search found this on another forum...
So I just changed my oil in the 800XC and the DR 6-fiddy I used Castrol Power RS Racing 4T from Canadian Tire. I bought just enough and thought I should have one on hand, but on my next visit to CT all they had was Castrol Power 1 4T. I asked the young fella at CT if they were the same and he had no clue, not surprising.
So I searched the web, not a real firm answer. I then sent an email to Castrol and they confirmed it is the same Power RS has been rebadged Power 1. Here is the response below.
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Thank you for contacting Castrol North America.
Castrol Power RS Racing 4T 5W-40, 10W-40 and 10W-50 oils have been rebranded to Castrol Power 1 4T 5W-40, 10W-40 and 10W-50 oils -- product specifications remain the same.
Castrol always recommends following the guidelines of the original engine manufacturer for the recommended oil for use in your specific application. This information can be found in the owner’s manual or by contacting the manufacturer directly.
Thank you again for contacting Castrol, we value your patronage!