I plugged in the Wolverine oil pan heater, the engine block heater, and the transmission pan heater for 35 minutes on the first freezing morning last week. With my pre-luber pumping the hot oil from the oil pan the dummy low oil pressure warning light dimished immediately before I cranked up the engine. I noticed the oil temperature reached 170F. As I drove the car the oil temp slowly dropped below 140F, the lowest reading on the gauge. I assume the oil was cooled off as it traveled to colder part of engine. But after 10 minutes of driving the oil temp came back to 140F and climbing. That was quite fast considering it usually took 15 minutes of driving for oil to reach 140F on a 76F morning without the use of any heating devices.
So, I am not sure if the Wolverine itself will be able to warm up the entire engine as the vendor claims without the help of an engine block heater under a freezing temp, but it definitely helps during the engine startup.