AdrianC wrote:
The other major factor is whether you're running a pipe of hot oil the length of the van or a single bit of wire. I know which I'd rather have a problem with in use...
Wrong, the oil in the tube is cold.
I'm sure you have heard of brakes and how they work, just in case you haven't, it's energy transfer, the fluid does not move, it merely transfers the energy.
Oh and mechanical gauges use heat protection if the tube passes any components hot enough to melt ptfe, just like the electric ones... which rely on electricity to work, and we all know about how troublesome that can be.