The big advantage to synthetic is cold starts, which would definetly apply to you in Canada. I am trying it for the extended drain intervals. Actually I am still on the fence with this dino vs, syn. debate. As they say "proof is in the pudding". I know someone who is the original owner of an '85 Ford T-Bird Turbo Coupe that currently has 190,000 miles on it. He has relgiously done 3K oil changes using Castrol 10W-40. My father owns an '85 300D with 320,000 miles and uses dino oil 10W-40. Neither has had any engine work done. As I mentioned in my previous posting, I am trying it as a time and money saver, using the synthetic.
BTW here in NJ I have only seen 15W-40 by Castrol at one place. The oils I can get just about anywhere is Mobil 1 products and Chevron Delo 400 15W-40 at any Walmart.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member