Forget the magnet--Get a glue on heater pad. They are offered by Kats --Zerostart-- Arcticfox -- Wolverine ETC. They are a flexable silicone hot pad you put on with Silicone sealant. They come in 25 thru 1000 watt and are the real Mcoy. All the auto stores here stock them , even the Wasilla Wallymart has them. We use them on EVERYTING! Even have one on my snow plow hydraulic unit . I have never had one burn out and their heat transfer is very efficent. Search the net with "oil pan heater pad"