Im am a driver and own my own truck. Got this unit to preheat my coolant as i live in Michigan.
Havnt had a chance to really test it much yet but after it running for 20ish minutes in 13degree weather the truck fired up and within about 3 minutes while idling along to the fuel island I had warmish air blowing through my vents. I imagine if I actually.let it run for an hour or so it'd be hot and the truck would fire like on a summer day.
Just keep.in mind this unit is rather large. I installed it horizontally in my passenger step box due to lack of frame space from auxillary equipment.