Is there really such a thing?

All kidding aside - for a mild 2-month Canadian winter you should be fine with a R134a conversion.

EDIT: I meant a mild 2-month Canadian summer...

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280