In Reply to: Magnetic Oil Pan Heaters posted by Larry on December 11, 2017 at 11:39:48:
I found engine block heaters work the best.
They replace the frasher plugs ( freeze plugs).
I have 2 300 watt plugs on the Ford 5000 diesel
I use a thermo cube to pick up a relay that feeds
The heaters. The thermo cube will not handle the
current draw of the heaters. The relay is fed from
a separate circuit.