EMS 40° F mummy

I often sleep in my North Face 0 F bag - I bought this bag for some warmer summer trips. I was disappointed with:

a:) the significant, quick loss of loft

b:) the inability of the bag to provide comfort in a 45 F environment, even though rated to 40 F. I was very cold on a 45 F night in the cascades, in mid-summer.

The bag is nice - it fits, it compacts, I've even gotten it wet on 55-60 F nights - but it is not as warm as EMS claims it to be.