This is the exact consensus of opinion regarding aircraft engines as well. In fact, most of us use engine pre-heat below 40 F for that very reason in planes, and the reason i posted the question here. BTW, i have looked at the owners manual. Minimal info on this subject there.

 

My 17 did not have the block heater option. Since I was going to MN on a regular basis to see my 92 YO Mom I decided an engine heater was in order. I did not feel like cutting a hose or knocking out an expansion plug or anything else that required actual work so I went for a walk on the internet. After 40+ years of fixing cars I limit my interaction with them so I looked for the easiest to install and the most likely to be the most beneficial. I even found it on sale at the price it sold for before the leveraged buyout. I do not remember who builds it but I loved the ease of installation and it’s ability to warm that which is most important, the engine oil. I drove my truck up on the ramps, pulled the lower panels, grabbed the heater off the floor, stuck it to the oil pan, tie strapped the cord so I could reach it from the top, reinstalled the trims, drove the truck off the ramps, finished locating the cord for easy access and called it a day. Neodymium magnets are a great thing and the truck fired right up on those wonderful -25F mornings. Hell, one morning it was so nice out that my relatively new extension cord broke in half.

 

Electric element oil pan heaters work, but you must be careful because the oil next to the element gets very hot and has a tendency to coke slightly. If using the heater on a regular basis you need to shorten your oil change interval.

 

I grew up in MN and learned a few things along the way and one of those is that having the oil coke from a pan heater is close to last on the list for reasons to shorten the oil change interval in cold weather.

 

Plug my truck at 20* , I have it on a timer and it kicks on 3 hours before I start it
Anchorage Alaska