I haven't yet got my fuel heating system set up the way I want it, as I'm still waiting on some motorised ball valves to arrive. In the meantime, yesterday I was talking to my mechanic about it, and he came up with a very attractive option. X5 beemers run a HE for the purpose of fuel efficiency - he tells me it gets over 100 degrees. It's an enormous unit - about the size of a brick - and works off electricity and coolant. When the engine is first started the electric elements do the heating, and the coolant takes over once the engine warms. But it seems to me that if it does indeed get over 100 deg then the electricity must be providing supplementary heating as well. He did a demo - he started the engine, and within 30 seconds the HE was too hot to touch.

Has anyone come across one of these before? He tells me they're easy to get 2nd hand and not too expensive.