Yes they'll start but you do drain alot of battery power and last year in january we had 26 straight days with temps -25 or colder batteries will not last under these conditions. Plugging in becomes nessceary

 

I have personally started an common rail truck in Thompson Manitoba when the thermometer said -34 with 20-25mph wind (around -60 wind chill) without plugging it in. It wasn't happy for the first 15 seconds, but it didn't stall.

It had good batteries and was prepped for cold weather (with Delvac 5 40 syn.)

Spudman is right, the batteries are key and are actually a little underspec'd for the application.

 

Exactly! I doubt if bigblock climbed under his truck to see if it had a muffler. Both Ford and Chevy diesel trucks come stock w/ the heater cord. Even rigs in Cali should come stock from the factory w/ the cord because the rig may very well end up in a cold climate. The engine will last much longer if maintained well, and this includes warm starts in cold climates. Remember that if DC charges us $10, the cord costs them half or less. This item, as well as wheel well liners should be standard on ANY $40000 rig, Ford, Cheby, and Dodge.

 

I wouldn't worry to much about plugging in either. I hadn't stated my truck for 6 days and it's been anywhere from -15 to +20 here in Wyoming and it starts right up without a hitch, and that's with only one grid heater cycle and 15-40 oil. No stalling, hiccups, etc. I love it.

The block heater in the Duramax is only standard in a few select states (about nine or ten of them I think), not even all the nothern states. In the others, it has to be ordered. I'm not sure about the Ford.

 

Ford also!

 

they are still standard equipment [the cord for the block heater] in canada iirc... for our cold climate