Mobil 1 in Canada is $32.84 for five litres (5.29 US quarts) or $7.54 for one litre bottles at most Wal-Marts. Most other retailers have it at $37.99 for 4.4 litres (4.5 US quarts) and $8.99 for one litre bottles.
Pennzoil Platinum is good stuff, but 5 quarts of Platinum for $30 versus 5.3 quarts of M1 for $33 is a tough pick. I would prefer the Platinum for everyday use in most conditions, but I use the Mobil 1 for its extreme performance on the low temperature end of the scale.
I am actually looking hard at Amsoil XL-7500. The thing is I still can't convince myself to do extended drains, I might be good for 12,000 km on a summer run, where it is fairly stable temperature with a lot of long distance running, but in the winter it's 5,000 or bust.
Right now the quest seems to be either for an exceedingly "high value" synthetic oil, something that may not be the best but is priced like a conventional so I don't feel so bad dumping it at 3200 miles, or a conventional that offers something performance wise that makes synthetic a wasted value proposition three seasons of the year.