block heater
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If not, I would not waste time pulling a expansion plug and putting an element in. Instead I highly recommend a circulating block heater, they do a excellent job!! If you can justify the cost, or just have extra cash kicking around (ha, ha), put a Webasto or Espar on your rig. They use diesel fuel to heat your coolant, no 110 power needed, and draws very little from you 12V system.
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