As I understand it, glow plugs work by heating the cylinders to aid starting. Once the cylinder is hot, the fuel ignites by compression. Surely the engine heats itself by doing this over a few cycles - so do the glowplugs stay on throughout the journey, or cut out after a short period? I suspect that is the case, but how long would that be?
This refers to a Mondeo TD, but I also suspect that is circumstantial.
Thanks!