Different kernels

[MR ZenWiz]

I recently installed 14.04.4 Xubuntu on my new work desktop, and it
has a 4.2 kernel rather than the 3.13 kernel on my older 14.04
installations.

I must have missed that announcement, but I'm curious as to why the change.

More importantly, how do I upgrade my fully up-to-date older 14.04
installations to get this kernel and its associated components?
They're all showing 14.04.4, but the kernel is 3.13.

Thanks.
MR