Intresting... I traveled for years and had a block heater.. Did replace the cord but never the heater... Was going thru boxes of stuff in the shop today... Came across a some what dirty unopened box.. Opened it and found an in line fuel heater..
A heat exchanger so to speak.. It has the fuel thru the center and the warm water from the engine on the out side.. Its a mercedes stock part.. Has all the instructions.. Ran those for years with the block heater to keep the fuel warm and after starting its warmed by the water going to the heater.. Worked great...... Sure have no use for it where I live.. Seldom goes below 0 here.. Have not heard about any one using those for some years..
Ken