I have a 2008 Outander 4 cylinder 2.4L. I know it's summer, but
I installed a cartridge style engine block heater today:

Zerostart 3100111

I chose the Zerostart over the equivalent Kats 11812 because the
Zerostart was cheaper and it came with a cap for the electrical
plug. Apparently there is an OEM part MZ314528 available in
Canada only (not the US).

I found this website useful:

Engine Block Heater Installation - MirageForum.com

but the installation is different on the 2.4L Outlander and the Mirage.

The Zerostart (Phillips & Temro) catalog and the part itself
lack any useful installation instructions. The internet/google
weren't any help to me either. It took me more than an hour of putzing
around to figure out where it goes. I almost gave up and returned
the part.

The heater slides in a cast hole in the engine block
on the side of the engine towards the left front wheel.

I'm attaching a photo taken shortly after the part was installed.
Look for the orange colored part. From the photo, you
should be able to figure out what you have to remove to
slide the heater into the cast hole any how to orient the
clip to hold the heater in.

The photo is taken from the front of the car; you can see the
red plastic covering the positive battery terminal on the
right side of the photo.

I recommend you drain the antifreeze first. I didn't, because
I didn't have any real instructions and I didn't do sufficient
research to know the heck I was disconnecting before I actually
disconnected it.

We never had any trouble starting the Outlander in winter (-25F).
I'm one of the people who believes there's a lot more wear
and tear on an engine when you start it in very low temperatures
because the oil is so thick.

Hope this helps someone considering installing a block heater.