oil 40w or 30w

for the winter should u put 30w inside of 40w in your 400? Mine wont start very well at all so i was wondering if this would help and i keep faling plugs what would make this happen? any other ppl have this problem

[Alberta EX]

My AMSOIL dealer told me to run 0w40 all year, up here in Canada

I went from 20-50 to 10-40 syn. with good results here in mich.