I am newbie to trucks.

How important is it to use the engine block heater? Last winter I got lazy and didn't plug it in. I only drove it a few times a week. It sits outside throughout the winter (Milwaukee, WI). It started OK.

What temperature do you recommend I use it?

Should I plug it in for a really cold night, then unplug it when it warms up during the day or leave it plugged in for some number of days at a time?

Thank you for your advice.

 

It is not necessary unless you live in Alaska or when it gets bitterly cold out (like -30F or below).

One thing I do recommend is getting a battery maintainer at those temps too.

 

I would only plug it in when needed, anything else is a waste of electricity. I did have to get a battery maintainer for my truck as suggested, as the battery will go dead or lose charge after a couple of months.

 

I agree I wouldn't use it all the time. It makes your electric bill go way up.
I only use mine when it's really cold, and I plug it in the night before I drive it. That's the only time I use it.
If you drive it several times a week, you shouldn't need a battery maintainer to keep the battery up.

 

When it gets down to -15 to -20 F, I would use it.

 

I park outside a lot in Minnesota. I plug in my 3.5 ecoboost whenever the temp goes below 15 or so. Say what you will about the tiny increase in power bill, but the truck warms up quickly, doesn't start as "hard" and it IS easier on the engine. There's a reason these vehicles have block warmers. I think you're right to use it, along with a battery tender if it's sitting. Another fun fact, these 3.5 block heaters don't just run in perpetuity. The engine heater only brings the block to just over 40 degrees, so even when I plug it in at home, I don't notice any significant bump in power bills.