i strongly dissagree with the castrol 0w30 in our climate. Again thats ME talking and My opinion only. But i would run 10w 30. it should take care of SOME of the ticks with these motors as well. and try not to think of it as weight, but as viscosity. the higher the number the MORE viscous the fluid.
http://www.upmpg.com/tech_articles/motoroil_viscosity/
so in this article. 0w Isnt a bad idea. it FLOWS better at colder temps(IE) colder engine. but to my experience it doesn't LUBRICATE as well at that grade. again my opinion Really and choose what you want.
and i would stop using mobil 1. they have downgraded to a tier 3 oil, castrol is still a tier 1 last i checked.